Add gepetto_hooks gemspec

Without this patch the dependencies in Bundler aren't resolving
properly.  This patch addresses the problem by allowing the library
itself to be referenced in bundle.
Update bundle gemfile and lockfile

Without this patch the bundle doesn't reference the gepetto_hooks gem.
This patch updates the gemfile to resolve dependencies.
Add bundle exec rake jobs:summary task

Without this patch we don't have an easy and automated way to summarize
all of the cards completed in a given time.  This patch addresses the
problem by adding a `jobs:summary` task.  This task will scrape all of
the cards in the `TRELLO_FINISHED_LIST_ID` column and create a summary
of the results.  It will use a Liquid template from
https://github.com/puppetlabs/puppet-webhooks/blob/templates/templates/trello_template.md.liquid
by default.

The URL may be overriden using `SUMMARY_TEMPLATE_URL` with the rake
task.  e.g. `bundle exec rake jobs:summary
SUMMARY_TEMPLATE_URL=http://jeffmccune.com/summary.template`
Update README
Make default RACK_ENV=test not production

This makes `bundle exec rake spec` work more cleanly out of the box
without having to explicitly state `bundle exec rake spec
RACK_ENV=test`.
Add completed job summary jobs:summary task

* completed_card_summary:
  Make default RACK_ENV=test not production
  Update README
  Add bundle exec rake jobs:summary task
  Update bundle gemfile and lockfile
  Add gepetto_hooks gemspec