Updating Gemfile to use HTTPS version of RubyGems.

Signed-off-by: Chris Schmich <schmch@gmail.com>
Merge pull request #13 from schmich/gemfile

Updating Gemfile to use HTTPS version of RubyGems.
Removed the .ruby-version file.

ffi-aspell doesn't really depend on a specific version so lets get rid of it.
Updated the contributing guides.