Xml serializer produces broken files

[mlooney]

It's an easy fix though, the namespace declaration for gexf is hosed up:

GEXF_ATTRS = {
    'xmlns'     => '"http://www.gexf.net/1.2draft',
    'xmlns:xsi' => 'http://www.w3.org/2001/XMLSchema-instance',
    'xsi'       => 'http://www.gexf.net/1.2draft http://www.gexf.net/1.2draft/gexf.xsd',
    'version'   => '1.2'
  }

See the messed up quote marks in the xmlns entry.