Getting a release of 1.7.1 ready.

Minimal changes to get the gem to load without warnings and the specs to run using
current versions of JRuby.
Version bump to 1.7.1
Regenerate gemspec for version 1.7.1
adding development gems to gemfile marks them as dependencies - this breaks applications that have conflicts with these gems. Putting the development dependencies in a different group so that jeweler does not pick them up