removed unused styles; added initial rio2013 styles

* removed unused European MetroMonitor / LSE Cities labs styles
* added initial rio2013 styles
* moved ec2012 styles to own subfolder
initial style tweaks for rio2013
fixed paths
updated rio2013 colours, moved common code to mixin
rio2013 header and footer
specificity--
twitter hashtag; level2nav colors
fixed background test
!squash fixed syntax
body opacity
tweaked opacities
hide heading image while testing image-heavy layout
MONKEYPATCH: column width override for tests
MONKEYPATCH: stretch image vertically
moved background image to pseudoelement
removed background image altogether - doing it via html elements
background images, initial styles for level2nav
level2nav cleanup, background img transitions
do not display background photo on screens <1024px
removed legacy test code