remove mongodb bits from documentation

[Will Kahn-Greene]

The documentation in docs/ talks about installing and configuring mongodb. That should be removed.

M=d2eab) saturn ~/projects/mediagoblin/docs/source> grin -i mongodb
./codebase.rst:
   85 :     ORM for MongoDB we're using which will make it easier to define
  151 : :models.py:  holds the mongodb schemas---these are the data structures
./deploying.rst:
  114 : Configure MongoDB
  122 : First, install MongoDB. On a DEB-based system run::
  124 :     sudo apt-get install mongodb
  128 :     yum install mongodb-server
  130 : After installing MongoDB some preliminary database configuration may
  133 : Ensure that MongoDB `journaling
  134 : <http://www.mongodb.org/display/DOCS/Journaling>`_ is enabled. Journaling
  135 : is enabled by default in version 2.0 and later 64-bit MongoDB instances.
  141 :    Running MongoDB without journaling risks general data corruption
  145 :    MediaGoblin recommends enabling MongoDB's journaling feature by
  149 : MongoDB can take a lot of space by default. If you're planning on

[Christopher Allan Webber]

Done!