Updates close button names

Updates close button related code to “clear” instead of “close” to be
more descriptive.
Merge pull request #585 from codeforamerica/update-close-btn-name

Updates close button names
Removes unused methods from util/util

Removes unused JS utility methods.
Merge pull request #584 from codeforamerica/remove-unused-util

Removes unused methods from util/util
Moves IE styles to their own override

Moves IE styles to their own stylesheet that appears last in the
sequence and is used to override the base styles with IE-specific
quirks. This allows:
- Removal of :after and :before selectors from the main stylesheet.
- Easier removal of legacy IE support, should that be removed in the
future.
Merge pull request #586 from codeforamerica/ie-style-separation

Moves IE styles to their own override
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
Fixes #573 - Browser upgrade alert

Fixes #573 - Displays dismissible upgrade alert for visitors that visit
with IE8. URL given in alert is https://browser-update.org/update.html.
Sets a cookie after alert is closed so alert isn’t displayed again the
same day. Cookie expires after 1 day.

- Implements addEventListener on alert component so observers can
respond to closing of the alert box.