Remove testing and support for Ruby 1.8.7

Closes #137.
Drop testing and official support for rails3 and rails 31.

Conflicts:
	gemfiles/rails3.gemfile
	gemfiles/rails3.gemfile.lock
	gemfiles/rails31.gemfile
	gemfiles/rails31.gemfile.lock
	gemfiles/rails32.gemfile
	gemfiles/rails32.gemfile.lock