Group reports by committers in text reporter instead of terminal notificator

* text reporter: group the report by committer.
* terminal notificator: never group the report by committer.
Add JSON reporter.
Add pendaxes-oneshot command for oneshot running.

Usage:

$ pendaxes-oneshot --help
$ pendaxes-oneshot ./spec
$ pendaxes-oneshot ./spec/a_spec.rb ./spec/b/**/*.rb
$ pendaxes-oneshot --quiet ./spec
$ pendaxes-oneshot -q -r json ./spec
Bump version
Merge branch 'oneshot'