Issue #6 (Startseite perfektionieren)

Issue #6

	modified:   app/assets/stylesheets/global_styles.css.sass
		* tested background modifications
	modified:   app/assets/stylesheets/nav.css.sass
		* altered hover state for teaser-box headline link
		* altered position of teaser-boxes
		* removed obsolete effects
	modified:   app/views/layouts/_nav.html.haml
		* removed link around teaser-box content

Issue #8

	modified:   app/assets/stylesheets/header.css.sass
		* increased header height
	modified:   app/views/layouts/_header.html.haml
		* added link to home

Issue #3

	modified:   app/assets/stylesheets/bootstrap_and_overrides.css.sass
		* added footer stylessheet
	new file:   app/assets/stylesheets/footer.css.sass
		* added styles for footer
	modified:   app/views/layouts/_footer.html.haml
		* added wrapping footer-tag