Retrieve the sourcecode for a method as a Ruby string

 The `method_source` is a utility to return a method's sourcecode as a
 Ruby string. Also returns `Proc` and `Lambda` sourcecode.
 .
 Method comments can also be extracted using the `comment` method.
 .
 It is written in pure Ruby (no C).
  - Some Ruby 1.8 support now available.
  - Support for MRI, RBX, JRuby, REE
 .
 `method_source` provides the `source` and `comment` methods to the
 `Method` and `UnboundMethod` and `Proc` classes.