At a Glance 6

-Changed link in usingMatchers user guide to point to atAGlance matchers section.
-Changed style traits choosing nav bar styling
-Added section links listing in beginning of atAGlance page
-Added print.css to exclude the style trait choosing nav bar and section links listing from being printed
-Refactored out sections in atAGlance into their own file
-Added check object's class matchers example
-Added check emptiness matchers example
-Some minor adjustments