Bump version back to dev
Add DOI to README
Fix violinplot with multiple identical values

Closes #368
Merge pull request #369 from mwaskom/fix_violinplot

Fix violinplot with multiple identical values
mask array gets reversed too
(copy and paste) documents "mask" kw in heatmap
heatmap: handles pandas and numpy masks
heatmap: narrows down exception type
Merge branch 'v0.5'
Merge branch 'heatmap-missing-fixes' of github.com:sdvillal/seaborn into sdvillal-heatmap-missing-fixes
Add test and release notes for heatmap mask fix