trying to loosen dependencies

I had a bit of trouble install jiralicous because its dependencies are so restrictive. It conflicted with my versions of httparty and json. There is no reason to keep them nailed down to a specific minor version since Travis supports building agains multiple gemfiles, allowing us to build agains the entire range of dependency versions.

I added ruby 2.0.0 to the gemfile.
I opted to test against the oldest dependency in one gemfile, and the newest that bundler can grab in the other gemfile. The versions in between should take care of themselves.
I also deleted .ruby-version since this is a library and not an application. Consumers will be running a wide variety of ruby versions.