tabindex on paper-text causes the focus to be invalid

[kitsunde]

Go here: https://miguelcobain.github.io/ember-paper/#/textfield focus on the first element. Tab through the input fields.

The first focus lands on the md-input-group which has a tabindex specified. You can't type on it. The second tab lands on the input where you can type. Effectively you have to double-tab to move between elements.

[miguelcobain]

@DanMonroe, please consider this. #120

[DanMonroe]

OK, I've got it fixed. I'll include it in my next push.