[Speed] Major speed improvement by using RollingCurl and parsing HTML directly

Two big things: 

  1. The tags are now parsed directly from the tags page via the Web interface. This is about twice as fast as using `svn ls`. I currently fetch all `li` items on the page and I doubt they will update their format soon.
  2. I added the [https://github.com/chuyskywalker/rolling-curl](RollingCurl) library which is a wrapper around [http://www.php.net/manual/en/function.curl-multi-init.php](PHP curl_multi). By default, it maintains 10 concurrent connections, but this is overridable via the `concurrent` option.

I saw dramatic improvements on my computer, using 10 connections, it was almost 15 times faster (including the 50% gain by directly parsing HTML).