feat(): Add jqm-theme directive, controller

for #31

In addition to #31, I also made it so the `html` directive gets the themeController, so things will always have at least a default theme.

This is still WIP because I'm not sure exactly how to test it ( I tested the controller, but not the directive ).  I left comments in the directives/jqmThemeSpec.js file about what I tried.