Log Message:
Update ruby-nokogiri to 1.6.0.  This is a new branch.  Changes:

1.6.0 / 2013-06-08

  This release was based on v1.5.10 and 1.6.0.rc1, and contains changes
  mentioned in both.

  Deprecations

    Remove pre 1.9 monitoring from Travis.

1.6.0.rc1 / 2013-04-14

  This release was based on v1.5.9, and so does not contain any fixes mentioned
  in the notes for v1.5.10.

  Notes

    mini_portile is now a runtime dependency

    Ruby 1.9.2 and higher now required

  Features

    (MRI) Source code for libxml 2.8.0 and libxslt 1.2.26 is packaged with the
    gem. These libraries are compiled at gem install time unless the environment
    variable NOKOGIRI_USE_SYSTEM_LIBRARIES is set. VERSION_INFO (also `nokogiri
    -v`) exposes whether libxml was compiled from packaged source, or the system
    library was used.

    (Windows) libxml upgraded to 2.8.0

  Deprecations

    Support for Ruby 1.8.7 and prior has been dropped