Add DashedRoute class.

Checkout the demand for dashed urls in #4755 in :smile: 
What is `dasherize`? :laughing: After looking, I see that Rails has this but, I don't think this makes a lick of sense. Sounds like a word from a Dr. Seuss book, haha. Shouldn't this class be `HyphenRoute` and this method be `_hyphenate()`?