Significantly optimize regexp time of fix_textareas!
Significantly optimize regexp time of fix_textareas!

The leading whitespace match and back reference added significant overhead in
certain cases, sometimes leading to render times taking minutes. In some cases,
the render time dropped from 2+ minutes to 200 milliseconds.

Closes #849

nazar-pc/haml,macressler/haml,nazar-pc/haml,keithpitty/haml,haml/haml,haml/haml,keithpitty/haml,tangposmarvin/haml,haml/haml,tangposmarvin/haml,haml/haml,macressler/haml