lib breaks on ruby 1.9.3 because of a regexp that is not compatible

There's been some changes to ruby's multibyte escaping rules since 1.9.3. In light of that, rkelly now has a SyntaxError when you attempt to use on 1.9.3.

```
`require': [..]lib/rkelly/visitors/evaluation_visitor.rb:318:
invalid multibyte escape: /(\A[\s\xA0]*|[\s\xA0]*\Z)/ (SyntaxError)
```

The solution to this is that regexes containing multi-byte characters must be explicitly marked as such. There is some discussion on [ruby-forum](http://www.ruby-forum.com/topic/183413) on how this should be marked. They mostly suggest using ```Regexp.new 'foo\xA0', nil, 'n'```, but I found out that the much more terse ```/foo\xA0/n``` would work just fine.