Create a CLI tool (for parsing, not editing)

[Tim Weber]

Currently, there's basically a proof-of-concept parser, and init.py simply displays their __str__().

I want a command-line tool with options like

• -f file: input file, or - for stdin
• -t tag: only display entries tagged with tag
• -i issue: only display entries associated with issue issue
• -a start, -o stop: only display entries in the given timeframe

Note that these options are not final, and even their names could change.

Also, we should be able to select from several output formats (text, JSON, …?).

We don't need everything at the first release though.