rubygems and bundler best practices

Hi,

this PR might be a bit presumptuous, but I started working on it so here it is:

I've noticed that the repo has Gemfile.lock checked in, which is, according to [the gospel](http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/) not recommended. This led me into the proverbial rabbit hole of rspec deprecations in current versions ending in actually removing one test that simply could not be written in a simple way with current rspec (and is actually kinda superflous). 

Please ignore this PR at will if you find this to be too annoying :)

Thanks,

Jan

- Moved development dependencies to gemspec, cleaning up Gemfile
- Removed Gemfile.lock (should not be checked in to git for libs/gems)
- Updated specs to remove rspec deprecation messages
- Removed test in opt_verify_spec.rb that was not working without deprecated rspec methods
  and was implicitly contained in the next spec anyway.