Large-screen style sheet for IE8- with Breakpoint, closes #100

Created a new file excelsior.oldie.scss that generates excelsior.oldie.css which contains the styles that would apply to a large screen, but without any media queries. This new CSS file can be conditionally loaded for IE8-.

**Note**: There is a known bug in Breakpoint which prevents this feature from working properly, so excelsior.oldie.css actually produces the same result as excelsior.css does now (mobile styles are applied, media query styles are not). This is due to be fixed in the next version of Breakpoint, so we should hold off on conditionally loading the new style sheet until then.