Feature add - SSL SocketFactory Configuration and Response Header Access

Hi all

I have added new capability of setting up a SSL socket factory for the rest client.  This is done via overloaded constructors.  This code required the addition of the Apache commons HTTP client libraries included in BuildConfig.groovy.  I have also added static convenience methods to create a 'fake' ssl socket factory, because dealing with self signed certs is pain!

Also I have added a helper method that allows for response headers to be accessed.  These changes are in RestResponse.groovy


All the new features have basic unit tests that I have added

I have also done a general cleanup of the unit test creating Spock shared resources.

The Grails version was upgraded to 2.3, and I removed the Spock dependencies since we don't need them in Grails 2.3.

Thanks

Chris