README: Add simple usage

let's add a very rough but practical usage guide to our README.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>

README.rst

@@ -3,4 +3,78 @@ Aexpect: Control your interactive applications
 
 This module provides services similar to the `pexpect` python library,
 so to speak, spawn and control interactive applications, such as `ssh`,
-`sftp` and others.
+`sftp` and others although it can be useful for pure streams as well.
+
+It's enhanced of multi-pattern matching, convenience features for
+not-only-linux terminals as well as support for terminals that "spit"
+extra output from time to time (eg. kernel messages) over the output.
+
+There are also extra classes to simplify executing parts of program
+on a different location (distributed programming) or writing controls
+executed on another host (metaprogramming).
+
+Simple usage
+------------
+
+.. code-block:: python
+
+    >>> import aexpect
+    >>> import time
+    >>> dir(aexpect)
+    ['Expect', 'ExpectError', 'ExpectProcessTerminatedError', 'ExpectTimeoutError', 'ShellCmdError', 'ShellError', 'ShellProcessTerminatedError', 'ShellSession', 'ShellStatusError', 'ShellTimeoutError', 'Spawn', 'Tail', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__path__', '__spec__', 'client', 'exceptions', 'kill_tail_threads', 'remote', 'rss_client', 'run_bg', 'run_fg', 'run_tail', 'shared', 'utils']
+    >>> session = aexpect.ShellSession("bash")
+    >>> session.cmd("ls /tmp/b")
+    '1  2\n'
+    >>> session.cmd("cat /tmp/b/1")
+    'Hello\n'
+    >>> session.cmd("cat /tmp/b/2")
+    'World\n'
+    >>> dir(session)
+    ['_ShellSession__RE_STATUS', '__class__', '__del__', '__delattr__', '__dict__', '__dir__', '__doc__', '__enter__', '__eq__', '__exit__', '__format__', '__ge__', '__getattribute__', '__getinitargs__', '__getstate__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_add_close_hook', '_add_reader', '_aexpect_helper', '_close_aexpect_helper', '_close_reader_fds', '_get_fd', '_join_thread', '_read_nonblocking', '_start_thread', '_tail', 'a_id', 'auto_close', 'close', 'close_hooks', 'closed', 'cmd', 'cmd_output', 'cmd_output_safe', 'cmd_status', 'cmd_status_output', 'command', 'ctrlpipe_filename', 'echo', 'encoding', 'get_command_output', 'get_command_status', 'get_command_status_output', 'get_id', 'get_output', 'get_pid', 'get_status', 'get_stripped_output', 'inpipe_filename', 'is_alive', 'is_defunct', 'is_responsive', 'kill', 'linesep', 'lock_client_starting_filename', 'lock_server_running_filename', 'log_file', 'log_file_fd', 'match_patterns', 'match_patterns_multiline', 'output_filename', 'output_func', 'output_params', 'output_prefix', 'prompt', 'read_nonblocking', 'read_until_any_line_matches', 'read_until_last_line_matches', 'read_until_last_word_matches', 'read_until_output_matches', 'read_up_to_prompt', 'reader_fds', 'reader_filenames', 'readers', 'remove_command_echo', 'remove_last_nonempty_line', 'send', 'send_ctrl', 'sendcontrol', 'sendline', 'server_log_filename', 'set_linesep', 'set_log_file', 'set_output_func', 'set_output_params', 'set_output_prefix', 'set_prompt', 'set_status_test_command', 'set_termination_func', 'set_termination_params', 'shell_pid_filename', 'status_filename', 'status_test_command', 'tail_thread', 'termination_func', 'termination_params', 'thread_name']
+    >>> session.sendline("for I in $(seq 10); do echo $I; sleep 1; done")
+    >>> session.read_nonblocking(0.1, 2)
+    >>> time.sleep(10)
+    >>> session.read_nonblocking(0.1, 2)
+    '2\n3\n4\n5\n6\n7\n8\n9\n10\n[medic@fedora ~ \x1b[1;31m\x1b[0m]$ '
+    >>> session.sendline("for I in $(seq 10); do echo $I; sleep 1; done")
+    >>> session.read_nonblocking(1.5, 2)
+    '1\n2\n3\n4\n'
+    >>> session.sendline("for I in $(seq 10); do echo $I; sleep 1; done")
+    >>> session.read_until_output_matches("3", timeout=10)
+    (0, '1\n2\n3\n')
+    >>> session.sendline("for I in $(seq 10); do echo $I; sleep 1; done")
+    >>> session.read_until_output_matches(["5", "7", "2", "foo"], timeout=10)
+    (2, '1\n2\n')
+    >>> session.cmd_status("true")
+    0
+    >>> session.cmd_status("false")
+    1
+    >>> session.is_alive()
+    True
+    >>> session.is_responsive()
+    True
+    >>> session.sendline("exit")
+    >>> session.is_alive()
+    False
+    >>> session.is_responsive()
+    False
+
+Debugging
+---------
+
+Using this even for purely bash-like constructs is good as you can leverage
+the python debugger to interactively walk your issues. Especially the
+`pydevd` project is great as you can debug code from multiple machines on
+in a single Eclipse to see concurency issues. Execution is as simple as
+`pip install pydevd` on all machines, adding
+`pydevd.settrace(eclipse_machine_ip, True, True)` directly into the code
+replacing the `eclipse_machine_ip` with IP address of the machine where
+Eclipse will be running (eg. 127.0.0.1 for localhost). The following `True`
+are to redirect stdout/stderr which is usually useful but sometimes might
+lead to issues. Then you need to start the python debugger inside Eclipse
+by entering debug view and starting the pydev server
+`pydev->Start debug server`. Now you are ready and simply execute your
+application the way you are used to, once it reaches the `pydev.settrace`
+line it will dial to the Eclipse server and show up in your debug view,
+showing the code you are debugging even though it's on a different machine,
+allowing you to single-step across multiple processes.