Add support for PATCH and DELETE methods

While Sphinx supports both the DELETE and the PATCH HTTP methods, the WSME extension doesn't.

All credit goes to Haomeng Wang, by whom the solution was suggested:
https://bugs.launchpad.net/ironic/+bug/1261917

Fixes #10
Merge pull request #11 from ifarkas/add_missing_http_methods

Add support for PATCH and DELETE methods