Add an option for enabling lower case urls

[mrahhal]

Self-explanatory, just like in mvc: RouteCollection.LowercaseUrls.

So that Router.action('Account', 'Login') generates /account/login with the option turned on, this way we can just write route values like we do in mvc without thinking much about it.

Also, for a route like Articles/{key}/Edit Router generates the route values uppercased no matter what I give it. And using something like Router.action(...).toLowerCase() is problematic for obvious reasons.

Thanks for the great library!