Updates modernizr custom build

Updates modernizr custom build to include html5-shiv and include all
core features used on the site. Custom build URL:
http://modernizr.com/download/#-fontface-backgroundsize-borderradius-box
shadow-multiplebgs-opacity-rgba-textshadow-generatedcontent-cssgradients
-input-inputtypes-geolocation-printshiv-cssclasses-addtest-teststyles-te
stprop-testallprops-prefixes-domprefixes-load

Performs minor code cleanup (trailing return, remove unused comment,
remove unused script).
Merge pull request #587 from codeforamerica/updates-modernizr

Updates modernizr custom build