md-datepicker does not focus forward to generated input element

[mcdwight6]

When tabbing through a form with custom-defined tabindex attributes, md-datepicker does not function as expected by selecting the internally-compiled input HTML element. Instead, the tabbing sets the focus the md-datepicker element itself, not the input field and neither does it focus forward to the input. The only way to input data into the date picker input field without clicking on the field is to cycle completely through the form, after which the datepicker input field is finally selected.

I've made an example on codepen

[mcdwight6]

Seems my PR didn't pass its tests. Not sure what the errors mean though. Was trying to implement a similar solution to the one closing issue #2113. Any ideas? The errors with Travis-CI start here if it helps.