Upgrade requirements for "pymongo" and "sphinxcontrib-httpdomain"

The new version of "pymongo" contains support for MongoDB 2.6 and better
support for Apache's mod_wsgi.

The new version of "sphinxcontrib-httpdomain" contains bugfixes for Python
2.6.
Merge branch 'upgrade-requirements'

* upgrade-requirements:
  Upgrade requirements for "pymongo" and "sphinxcontrib-httpdomain"