Improved UI and improved jQM 1.4 compatibility

Hey Jonathan,

I've been using this plugin for a while. Now that we're upgrading our app to jQM 1.4, this plugin had to be upgraded as well. I didn't really like the UI of the current version, so I've tried to improve it.

In jQM 1.4, there's an [official workaround](http://demos.jquerymobile.com/1.4.3/controlgroup/#Textinputs) to make controlgroups containing text inputs. I've implemented this, and IMHO it looks better than the current UI.

Furthermore I made two other minor changes (which are documented in the commit messages).

Cheers,
Jonathan

P.S. I might try to make the textinput look more like a normal textinput (e.g., by having a white background). If the result is nice I'll make a PR for that as well.