Feature/fix multi theme select

[xmeng1]

Try to fix the bug #4077 for Input/Select/Slider/Tabs

I have converted the '&' in SCSS for input/select/slider/tabs and I have tested on my demo (use build of myself)

Demo:
https://ng2-material-admin.firebaseapp.com/
Demo repo:
https://github.com/xmeng1/ng2-material-admin

The build repo
https://github.com/xmeng1/material2-builds

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[xmeng1]

I signed it!

[googlebot]

CLAs look good, thanks!

[xmeng1]

I just see that @crisbeto has fix it. sorry.

[jelbourn]

Yeah, @crisbeto already added a fix for this and a lint check to ensure it doesn't happen again- thanks anyway!

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