Remove the git fallback
Remove the git fallback

The git submodule is removed as of #1850.

This was added by me in #874 to support node-sass being installed
as a gitish via GitHub rather than the npm registry.

We publish the LibSass src to npm already so it should continue
to work as is.

Smartbank/node-sass,sass/node-sass,saper/node-sass,Smartbank/node-sass,sass/node-sass,sass/node-sass,xzyfer/node-sass,saper/node-sass,xzyfer/node-sass,Smartbank/node-sass,saper/node-sass,Smartbank/node-sass,xzyfer/node-sass,nschonni/node-sass,nschonni/node-sass,xzyfer/node-sass,Smartbank/node-sass,sass/node-sass,sass/node-sass,xzyfer/node-sass,nschonni/node-sass,nschonni/node-sass,sass/node-sass,saper/node-sass,xzyfer/node-sass,nschonni/node-sass,nschonni/node-sass,saper/node-sass,Smartbank/node-sass,saper/node-sass,Smartbank/node-sass,xzyfer/node-sass,nschonni/node-sass,saper/node-sass,sass/node-sass