Changed API to now only use a case statement construct.

The case statement looks like:

    case recovery
    when RecoveryClass
      ... code
    when RecoveryClass
      ... code
    else
      raise
    end

What I'd really like it to look like would be:

    raise
    recovery RecoveryClass
      ... code
    recovery RecoveryClass
      ... code
    end
Removed the arguments parameter from the Recovery class.
This will be left up to subclasses to take arguments and expose attributes.
Added support for passing args when calling a Recovery and
receiving them from a recover clause.
Added generated documentation to the recoveries returned from an
Exception. This is suitable to display in Pry.
Removed unused Unsupported Exception.
Updated Readme to reflect new syntax.
Fixed failing test case on older rubies.
Fixed issued with less-supported Rubies.
Merge pull request #13 from michaeljbishop/case-syntax

Changes API to case-syntax