Allow jade options to be passed through

I have kept your defaults if no options are passed, and added one more – `compileDebug: false` which provides better error handling in node when true, but screws you in the browser.

I have added a test for this and also made a slight change to your other tests so that they check the compiled template is a valid function and return a non-empty string. This will make it less brittle if jade's output ever changes.