Clean misc files

Thank you for awesome framework.

When I have checked this repository because I want to use this in production, I found a not good files for other contributors.

I cleaned some misc files which is following
1. Remove unnecessary rule for ordinary rubyist in ".gitignore" and add basic rules.
2. Export the dependencies of development environment from Gemfile to gemspec.

The first thing is removing rules for Clojure-lang, second thing is following the gem developer's manner.
Please check http://docs.rubygems.org/read/chapter/20#dependencies.