Merge pull request #6 from myun2/develop

MessageBox call Implemented #4
Version to '0.0.1alpha.1' (Release for MessageBox)
fix gemspec.

require_paths and etc.
Create MessageBox.md
Update README.md
Gemfile.lock update
Merge branch 'master' of github.com:myun2/ruby-game-win
message_box: RDoc, and style_to_i.
MessageBox: Implement options.
yes, no, cancel, retry (MessageBox)
fix yes/no
fix RDoc (MessageBox)