Fix #14

Fix #14: history operations were being applied twice.

Enable output formatting

$ calc -u "0o644 | 0o111 :#o"
0o755
$ calc -u '0o755 & !0o111 :04o'
0644

[0]: 0xab :b 4
1010 1011
[1]: @[0] >>> 4 :x_4
b000_0000_0000_000a
[2]: @ & 0xF :4b
1010

$ calc pi / 3 :v#04.4
0d01.0471

Update installation instructions, create changelog

Still establishing project infrastructure.

Publish on crates.io

Take over the crate name from its squatter.

MVP

• performs all advertised operations
• respects hierarchy of operator precedence
• expression mode and shell mode
• automatic release CI
• reference documentation

There's a lot more coming, but this is enough to be useful.