Generate HTML JUnit Reports

[jonnyreeves]

We could merge in the functionality from https://github.com/phtrivier/grunt-junit-report which would allow us to spit out HTML reports if the user has an XSLT processor on their system.

@phtrivier would you have any objections to this?

[jonnyreeves]

OK, so I've started hacking away on this; pretty hack and slash so far but HTML reports are being generated via the system's local xsltproc; I did consider the libxslt node module, but it has c extensions which are painful to use in some environments (and being able to specify a path to a local xsltproc binary is easier ;).

https://github.com/jonnyreeves/grunt-qunit-junit/tree/feature/html-report

This is clearly going to require a fairly large refactor of the codebase; however I think the benefits are pretty tangible.