Admin CSS/JS: use `dpa_get_version()` for the version number for the enqueues, rather than hardcoded.
Tweak grunt watch:css command

Symlinks + PHP + WordPress continues to suck
Flatten a couple of the custom admin styles for the brave new 3.8

This is just a very quick improvement. A full admin UI pass will happen
at some point.
Immediately ping heartbeat on page ready.

This change increases the minimum WP version requirement of the plugin
to WP 3.8.