graceful degradation of banner logo for IE8 and below.
Merge branch 'improve_banner_logo_resolution' into gh-pages

Conflicts:
	banners.css
added larger banner logo.
Merge branch 'gh-pages' of github.com:ucsf-web-services/ucsf_identity_web_banner_templates into gh-pages
generated SVG from logo PNG
use SVG as background image instead of PNG
Added higher resolution logo PNG.
created higher rez SVG logo.
resize SVG logo for mobile.
replaced huge/unused PNG with fallback logo.
tweaked CSS to go along with image name chnges.
Merge pull request #8 from stopfstedt/improve_banner_logo_resolution

Improve banner logo resolution