Small updates to the doc.

Give a sample configuration file and warn about the execution time of
the metrics command.

docs/configuration.rst

@@ -64,3 +64,23 @@ Each section must have two keys:
 Note that even if you use a single token to access several repositories
 (possibly all your repositories), the token must be explicitly specified in each
 configuration section.
+
+
+Sample file
+===========
+
+Here is a sample configuration file for GrainyHead:
+
+.. code-block:: ini
+
+   [default]
+   repository: https://github.com/gouttegd/grainyhead
+   token: ghp_XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+   
+   [bio]
+   repository: gouttegd/biopython
+   token: ghp_YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY
+
+With such a file, calling ``grh -s bio`` will make any subcommand work on the
+*Biopython* repository. Calling simply ``grh`` will make the subcommands work on
+the *GrainyHead* repository.

docs/metrics.rst

@@ -24,6 +24,13 @@ during the reporting period:
 In addition, it also collects the number of individual contributors that caused
 those events to occur.
 
+Note that to gather those informations, the ``metrics`` command has to download
+a potentially large amount of data from GitHub. Those data are cached on disk to
+make subsequent calls faster, but the first time the ``metrics`` command is run
+on any given repository, it can take several minutes for the command to complete
+(depending on the size of the repository and the quality of the network
+connection).
+
 
 Default report
 --------------