fix(dialog): fix dialog alignment in IE

[jcruz2us]

Closes #790

I ran into this issue in IE10 and IE11 and I found a simple solution; Remove margin auto from the md-dialog element. After removing the margin, the dialog is properly aligned in Chrome, Firefox and IE10/11

[googlebot]

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[jcruz2us]

I made these changes. I'm resubmitting with correct email info

[marcysutton]

This is no longer applicable.