mitchellh/vagrant — pull request #3746 by Sharpie (2014-05-10 18:42:56+00:00)
Title: Speed up nokogiri installation during Travis runs

Version 1.6 of Nokogiri builds its own copy of libxml2 during installation.
Setting `NOKOGIRI_USE_SYSTEM_LIBRARIES=true` skips this step and shaves about a
minute off of Travis runs.