Use JSX within test files

[cutandpastey]

I'm starting to get confused when constructing trees to test. We should probably think of pre-processing the test files so we could use JSX. A incredibly brief search found me this: https://github.com/Raynos/mercury-jsx I'm open to other implementations if there are any that are better.

[robinedman]

I think this sounds like a good idea. mercury-jsx is probably a good choice as we're using part of mercury already (all the virtual-dom libraries).