Only set optional Oauth params if they're set in config.

Don't add oauth_callback or oauth_verifier from the oauth config array to paramsToSign unless they are set. This prevents them being duplicated if they are set as parameters for a function in a service description.
Fixed odd indentation

Fixed odd indentation
Merge pull request #356 from Danack/patch-1

Only set optional Oauth params if they're set in config.