Added cssmin, imagemin and concat and minify of the global.js file

Running "$ grunt build", will make an minified copy of global.css as
global-min.css, optimize all images in the images folder, and
concatenate and minify the global.js file into optimized.js.
Changed bower component folder to something less specific
Merge branch 'template' of https://github.com/g-kanoufi/YeoPress into template-develop

Conflicts:
	Gruntfile.js