Version 0.7

This is a minor release (not a patch) because it may (and most probably will) break backward compatibility with Ruby 1.8

* Drop support for Ruby 1.8 and add support for Ruby 2.0 and 2.1
* Fix a regression in Rails ~> 3.2.16 and ~> 4.0.2
* Fix Travis builds
* Update some deprecated Rspec method calls