rbeautify as a beautifier for ruby
Markdown now states about added ruby beautifier
Use &shiftwidth only when &expandtab option set
Added ruby sample
Added description to default formatprograms
Corrected gem name
Merge branch 'veelenga-ruby-beautify'
Added note about compatible ruby version

 * `rbeautify` for __Ruby__.
 It is shipped with `ruby-beautify`, which can be installed by running `gem install ruby-beautify`.
-Note that compatible `ruby-beautify-0.94.0` or higher version.
-Here is the link to the repository: https://github.com/erniebrodeur/ruby-beautify
+Note that compatible `ruby-beautify-0.94.0` or higher version.
+Here is the link to the repository: https://github.com/erniebrodeur/ruby-beautify.
+This beautifier developed and tested with ruby `2.0+`, so you can have weird results with earlier ruby versions.

 How can I change the behaviour of formatters, or add one myself?
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