Core: Respect non-error aria-describedby and empty hidden errors

Ref #1083
Closes #1140
Additionals: Fix $/jQuery usage, only use $ reference

Fixes #1180
All: Remove closing slash on empty elements
Test: Removes stale and useless test files and firebug light
Demos: Fix markup in captcha and marketo demo

Ref #1159
Ref #1185
Build: Update jscs, remove rules now included in the jquery preset