Losslessly compress osscdn-logo.png.

Before: 18520 bytes
After:  11712 bytes
Add frontend/app/data to .gitignore.
Make the browser prompt show in IE < 9.
Update html5-boilerplate to the latest git.

Remove unused html5 boilerplate files, unused classes and the Google Analytics snippet.
Use the minified JS files.
Add meta keywords and description.
README.md: remove SASS reference since it's been removed.
Fix a couple of CSS issues.

* merge duplicate selectors
* remove duplicate properties
* fix `cursor` property in `.sort`
* add `cursor:pointer` in `.displayHelp`
* remove `outline:none` when no other visual change is made
Use a `<p>` for the footer text.
Losslessly compress the Base64 PNG image for search.

It's 1/3 of its original size, for free.