little more cleanup prior to gem-build

- removing some files from source-control suggested by this [1] article
- moving version out into a separate file
- removing debugger from development depenedencies. folks can install
  and run that themselves if they really need it
- moving gem depenedencies into gemspec as oposed to them being
  duplicated between the Gemfile and gemspec

[1] http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+KatzGotYourTongue+%28Katz+Got+Your+Tongue%3F%29