Added to RestInvocation.getHttpMethod() to allow creation fully secure H...

Hi Matija I use an HMAC scheme with a REST api. The scheme includes the HTTP method in the signature. To make this possible, I added getHttpMethod() to RestInvocation.

I also added .DS_Store to .gitignore. I develop using OS X, and the Finder can create this file.

Hope you can pull.

Big thanks, Dominic