Update README with usage and requirements info

I'm just about to start hacking on Twig. I've discovered it requires
Ruby 1.9 or above, so note that in the README; also add brief usage
information to the bin/commit-stats section, and a note about setting
RUBYOPT for use with Rubygems.

Change-Id: Ib87ab428fc42867d6a372b638b9f101916a861b9
Reviewed-on: https://gerrit.causes.com/24871
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>
Add LICENSE

This is the standard MIT license that we use in most of our open source
projects.

Change-Id: Id82755079bace6f3752fbda32def83f7e5fcc8d9
Reviewed-on: https://gerrit.causes.com/24872
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>
Add -h and --help switches to bin/commit-stats

Change-Id: Ie0a8b4236af42b406cccefa124f17c7085c1fd98
Reviewed-on: https://gerrit.causes.com/24873
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>
Apply style fixes to bin/commit-stats

This is just for consistency with our conventions in other codebases:
breathing room around/inside curlies, and favoring single quotes over
doubles.

Change-Id: I4e69a1161304ff714c85599e8f2a17156af959bb
Reviewed-on: https://gerrit.causes.com/24874
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>
Update bundle

We were seeing segfaults with the version of Rugged that we were using,
so we've updated the bundle, bring it from 0.16.0 to 0.19.0.

One minor date-related tweak required to remain compatible with Rugged.

As a bonus, minor bumps to Haml and Sinatra included.

Change-Id: I43715db2e711a2c12845b8fdeea5e67ef765db8b
Reviewed-on: https://gerrit.causes.com/24875
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>
Use YAML.load_file rather than manually reading file

Change-Id: Ib023e5e1442f6aa96cca4cf4bfbda0db3cec355b
Reviewed-on: https://gerrit.causes.com/24879
Reviewed-by: Greg Hurrell <greg@causes.com>
Tested-by: Greg Hurrell <greg@causes.com>