fixed motif distances so they don't crash if a motif doesn't exist
Merge branch 'dev' of https://github.com/YeoLab/clipper into dev
fixied failing tests (that were failing as a result of an attempt to make clip_analysis more robust) and added in the option to output any file format as a result file (figure can now be enbeded in the ipython notebook), should eventually change to just allowing total control over output files...