Remove unused gems; don't load assets group in CI.
Remove explicit load of diff-lcs.

It's a dependency of rspec-expectations.
Only use the 'debugger' gem in development.

Installation was failing on Travis CI causing spurious failed builds, so
we don't want it under the test environment. I reckon we don't want it
in the production environment anyway.
Use unicorn instead of Thin webserver

This is in the name of eliminating unnecessary differences between
development and production. You must invoke unicorn with `unicorn`
rather than `rails s`. By default it listens on port 8080.
Don't load the "development" gem group on Travis CI.
Remove watchr continuous-testing gem.

Nobody was using it :-(
Document what CanCan does in Gemfile.
Document the :assets group in Gemfile.

I think we can probably delete some of it (in particular compass-rails),
but don't know how to test it. Halp plz?
Document gems in test group
Upgrade debugger to 1.6.0

This should now include the headers for Ruby 1.9.3-p429 whose absence
was causing our builds to fail. Better late than never...
Merge pull request #241 from pozorvlak/fix-travis

Fix travis
Merge pull request #240 from pozorvlak/gem_decruft

Remove some cruft from our Gemfile
prettified some of the error messages
Merge pull request #242 from Skud/cancan-messages

prettified some of the error messages