Support adding CSS class to MdDialog root element

[xtianus79]

Bug, feature request, or proposal:

Bug / Feature

What is the expected behavior?

Unlike The toast notifications which has a parameter to add a class... There is nothing I can add on the parent container level to change styling of md dialog.

What is the current behavior?

I can just override material styles

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

2.0.0-beta.2

Is there anything else we should know?

Nope

[fxck]

#3472

[xtianus79]

@fxck and @jelbourn as of right now this is not available? Or it is on beta.3

[jelbourn]

This exists now