New camelize filter #77

The [underscore implementation](https://github.com/epeli/underscore.string/blob/master/camelize.js) you linked is very simple. I've used [this one](https://gist.github.com/vjt/827679) instead, we can tune it a little bit to obtain what you need and eventually add a parameter as in the [Ruby implementation](http://api.rubyonrails.org/classes/String.html#method-i-camelize).