dmnfarrell/pandastable: v0.8.0

Adds some miscellaneous improvements. Grouped plots now work better, see http://dmnfarrell.github.io/dataexplore/2017/07/05/grouped-plots. A datetime conversion dialog has been added as shown in http://dmnfarrell.github.io/dataexplore/2016/11/20/sea-ice-example.

• Added datetime conversion dialog
• Changes to make more compatible with matplotlib 2.0
• Can now plot grouped single plots for some plot types (line, bar, scatter)
• Fixed sharey, sharex for grouped plots
• Added ability to choose pre-defined mpl styles
• Fix to memory leak on redraws
• Changes to right click copy behaviour in table
• snapcraft.yaml to create snap package
• Fix for displaying small floats that were rounded to zero
• Added floating precision to table preferences
• Clipboard bug fix
• Improvement to merge dialog
• Fixes to widget styling issues on linux
• Added duplicate column removal in clean data