HTTP method names are checked case-sensitive at the client
Add the method to Access-Control-Request-Method if it wasn't send in uppercase by the client
See http://stackoverflow.com/questions/9649972/firefox-overwrites-custom-http-method-link-to-mixed-case-link-on-xhr and http://annevankesteren.nl/2007/10/http-method-support

Fixing
Merge pull request #20 from SimonSimCity/master

Do not transform method-names, they're case-sensitive