robust version importing in docs build config

After changing sys.path, synnefo and synnefo.versions must be reloaded
because if they have been cached, the updated sys.path will not be
consulted because importing synnefo and synnefo.versions will stop at
the cache in sys.modules

docs/conf.py

 import sys, os
 
 sys.path.insert(0, os.path.abspath('../snf-cyclades-app'))
+import synnefo
+reload(synnefo)
+import synnefo.versions
+reload(synnefo.versions)
 from synnefo.versions.app import __version__
 
 project = u'synnefo'