Dialogs are not repositioning correctly when window is resized.

Please include the following information with your bug report:

> What MDL Version are you using? (please be specific, e.g. _major.minor.patch_)
1.3.0

> What browser(s) is this bug affecting (including version)?
Google Chrome v60.0.3112.101

> What OS (and version) are you using?
Windows 8.1

> What are the steps to reproduce the bug? Can you create a plunker/codepen/jsfiddle which reproduces it?
https://codepen.io/Garbee/full/EPoaMj

> What is the expected behavior?
When resizing the window should automatically reposition the dialog horizontally and vertically.

> What is the actual behavior?
When resizing the window, the dialog re-centers horizontally but not vertically.

> Any other information you believe would be useful?
The issue happens on my Android Chrome browser as well. I didn't test other browsers.