Add "Push and pull" documentation about office-ui-fabric-core

[Jahnp]

You're totally right, this (and the grid in general) should be better documented. Thanks for the catch--we'll get on it asap!

[andrewconnell]

Could we get a little clarification on what the syntax should be? I've got a Plunker that demonstrates how one would expect it works... but definitely have something wrong.

http://plnkr.co/edit/Yej1sF16nCsK7Wv5zzbY

[dkreitz]

I think I've got it figured out. The use of Push or Pull only shifts the column right or left respectively by the number of 12-column units. You still need to give a width to the column by using the ms-u-* column size classes.

Here's a fork from @andrewconnell code with what I believe is the solution.
http://plnkr.co/edit/tVIK2ZBSKMaytu1H1bSC

[andrewconnell]

LGTM

[ericthompson]

You've got it, @dkreitz! We've got our official interactive documentation site up that includes an image to help explain it. If this is still a bit lacking, let us know. Thanks!