Updates to comply with best practices for gem development outlined by Yehuda Katz (http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/).
Fixes errors (TravisCI requires that `rake` be in the Gemfile and the .travis.yml file specifies that the gems be installed without the development group, which excludes development gems specified in the gemspec.)
RUBY_ENGINE is undefined in MRI 1.8
Merge pull request #16 from DomKM/master

Updates to comply with best practices for gem development outlined by Yehuda Katz...