Replace jeweler with bundler
Fix deprecated error: rake/rdoctask => rdoc/task
Replace rcov with simplecov

Rcov doesn't run on 1.9+, but simplecov is a good replacement. Coverage
reports are now generated automatically with `rake test'.

I also removed the empty unit test in `test/helper.rb' too.
Merge pull request #4 from jmdeldin/move-devel-to-19

Update development environment for 1.9