Update to maruku 0.7

I do not believe there's been any major API change, AFAIK

[Maruku Changelog](http://rdoc.info/github/bhollis/maruku/master/file/CHANGELOG.md)

Gemspec now asks for 0.7.0 (final), which has been released.

It has changed some output behaviour after transitioning to its own output engine.

The parser will now do a `.strip` to take out any newlines Maruku has added surrounding html produced.

It now produces `"` for attribute (`src`) quotes and uses the !CDATA tag inside script so that it will produce valid XHTML.

I updated the tests to account for these.