Merge pull request #181 from brixen/master

Changes to pass tests on Travis with Rubinius
Version bump to 1.2.4
Ignore `Gemfile.lock`.

It is not good practice to check in `Gemfile.lock`
for a gem. The only use of `Gemfile.lock` is for a
gem developer _or_ an automatic build/continuous
integration. And since travis-ci builds for different
platforms, a single `Gemfile.lock` actually works
counterproductive.
Regenerate gemspec for version 1.2.4
Fix dependencies: they should be for development only.
Version bump to 1.2.5
Regenerate gemspec for version 1.2.5
Update History.

I should do this more often. Doh.
Removed Jeweler and created modern .gemspec.

The cocoon.gemspec generate by Jeweler was including the rubysl gems. This
causes cocoon to fail to install on MRI right now (see eg this stackoverflow
post: http://stackoverflow.com/questions/20390594/rails-gem-install-error-coccon)

Jeweler was also emitting redundant dependencies for rspec and emitting a
dependency for actionpack despite that the dependency on rails would pull
in actionpack.

To replace the Jeweler-generated cocoon.gemspec, I added one created by
Bundler and migrated the settings over. It is a simple matter to keep this
gemspec current by hand.