Fix the tests rul
If we are being passed an image size, and there is no "overloaded args" for that image size, there is no point in making a wpthumb image out of it
Watermarking tests were using the wrong option name
Tests for izes should make sure we _don't_ have the cache dir in them
Merge pull request #86 from humanmade/fix-86

Interfering with normal image insertion