Attempt to address multiedge difficulties in convert.py using from_dict_of_dicts: - changed from_dict_of_dict to operate on G.dj directly instead of through add_edge()      This allows multiedges to be converted without too much hassle.
Attempt to address multiedge difficulties in convert.py using from_dict_of_dicts:
- changed from_dict_of_dict to operate on G.dj directly instead of through add_edge()
     This allows multiedges to be converted without too much hassle.

While in there, I also:
- centralized the preparation of create_using to a routine convert.prep_create_using()
- changed some docstrings and removed ==True in if statements.
- put in warning comments that looking for "multiedge" attributes isn't very good for
  finding out if there is edge_data.  Somenoe could make weightedgraph without multiedges
  and it wouldn't work for that case.  Still thinking about how to test for edge_data...
- replace try/except with if for from_scipy_spase_matrix

--HG--
extra : convert_revision : svn%3A3ed01bd8-26fb-0310-9e4c-ca1a4053419f/networkx/trunk%40526

jakevdp/networkx,harlowja/networkx,jfinkels/networkx,kai5263499/networkx,ionanrozenfeld/networkx,JamesClough/networkx,harlowja/networkx,RMKD/networkx,goulu/networkx,blublud/networkx,chrisnatali/networkx,andnovar/networkx,farhaanbukhsh/networkx,kai5263499/networkx,beni55/networkx,dmoliveira/networkx,blublud/networkx,ionanrozenfeld/networkx,jni/networkx,farhaanbukhsh/networkx,chrisnatali/networkx,ghdk/networkx,michaelpacer/networkx,aureooms/networkx,nathania/networkx,bzero/networkx,nathania/networkx,jtorrents/networkx,debsankha/networkx,ltiao/networkx,farhaanbukhsh/networkx,SanketDG/networkx,sharifulgeo/networkx,debsankha/networkx,Sixshaman/networkx,kernc/networkx,aureooms/networkx,bzero/networkx,wasade/networkx,jni/networkx,harlowja/networkx,dhimmel/networkx,ghdk/networkx,yashu-seth/networkx,kai5263499/networkx,jakevdp/networkx,chrisnatali/networkx,aureooms/networkx,OrkoHunter/networkx,jni/networkx,kernc/networkx,sharifulgeo/networkx,dmoliveira/networkx,RMKD/networkx,blublud/networkx,dhimmel/networkx,NvanAdrichem/networkx,jcurbelo/networkx,kernc/networkx,sharifulgeo/networkx,RMKD/networkx,jakevdp/networkx,dmoliveira/networkx,cmtm/networkx,bzero/networkx,ghdk/networkx,debsankha/networkx,dhimmel/networkx,ionanrozenfeld/networkx,tmilicic/networkx,nathania/networkx,jtorrents/networkx