Set tabindex in custom component

[BobBDE]

Bug, feature request, or proposal:

Feature

What is the expected behavior?

Be able to set the tabindex to customs components (like md-slide-toggle)

What is the current behavior?

The tabindex are ignored by the customs components and thus the automatic tabindex is used.

What are the steps to reproduce?

Here is a simple plunkr that show the problem. Focus the first toggle button and click tab. The last one should be focused as it has the property tabindex set to "2".
http://plnkr.co/edit/V4q7uy?p=preview

What is the use-case or motivation for changing an existing behavior?

Be able to change the tabindex or remove an element from tabindex.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

All

Is there anything else we should know?

No.

[jelbourn]

We should accept a tabIndex for each of the interactive components. We currently do this only inconsistently.