A re-implementation of the 'insert matching end' for ruby.

[ognen]

Based on the previous pull request, this one fixes the following issues:

A couple of notes:

Should this be mapped for "source.ruby" and not just "source.ruby.rails"?

It doesn't insert "end" if there is a following "end", even if there is another "opening" keyword. For example:

def bar
|

def foo
"foo"
end

I would expect an "end" keyword after having pressed after "def bar". I guess it finds the "end" keyword for "def foo". This might not be easily fixable, though.