WIP 0.4.6 Release

[ejolly]

Changes for new release

1. Support multiplication from the left (only with lists!)

2. Dramatically speed up Brain_Data.similarity and support rank correlation #308 #316 #404

3. Add tests for Design_Matrix.clean and prevent use with Design_Matrix has duplicate column names

4. Incorporate PR #401 :

   # User loads h5 that contains mask so that mask is used instead of the default MNI mask
   
   Brain_Data('brain.h5')
   
   # User loads h5 that contains mask but also sets mask argument.
   # Now mask value takes precedence over whatever mask is in h5 
   # so we issue a warning to the user letting them know on load
   
   Brain_Data('brain.h5', mask='path/to/nifti/mask.nii.gz')
   
   >>> UserWarning(...)
   
   # User loads h5 that does NOT contain a mask and doesnt set the mask
   # argument so the default MNI mask is used, similar to nifti files
   # This is an implicit fallback just like with niftis 
   
   Brain_Data('brain_nomask.h5')
   
   # User loads h5 that does NOT contain mask but also sets mask argument
   # Mask value is used to learn transformation like niftis
   # No need to warn them about anything
   
   Brain_Data('brain_nomask.h5', mask='path/to/nifti/mask.nii.gz')
   

5. Fix weird formatting issues for some API docstrings