Initial commit of bar chart labels.
Merge branch 'develop' into labels-on-rects
Change code so things work as intended
Add needed API point
Sorry for doing so much in a merge commit.

Conflicts:
	plottable.d.ts
	src/components/plots/clusteredBarPlot.ts
	src/drawers/rectDrawer.ts
Fix tslint errors.
Now if any bar is too narrow, labels hide on all bars (even for plots with many drawers)
Correct license info for Chroma
Implement animation timing improvements:
- Drawsteps now execute in sequence, asynchronously; they wait for the previous draw step to finish before starting the next one
- Draw now returns the total time taken for all draw steps
- additionalPaint now recieves max time taken across drawers (ie duration of paint fn)
Updated draw timer management:
- Animators have a `getTiming` method which returns time to complete animation.
- Drawers return how much time they will take to finish drawing
- AdditionalPaint is immediately called with relevant timing info.
Take Brandon's feedback into account
- Rename RectAndText to Rect
- Split API into two points: enable & set formatter

Also, move text drawing into additionalPaint and out of regular Rect drawing.
Merge branch 'develop' into labels-on-rects
Fix some bugs that cropped up, rename variables to be more sensible
Use a CachingCharacterMeasurer for perf
Remove commented line from plottable.css
Add some unit testing
Address more of Brandon's comments
Address Andrzej's concerns and enhancements
minor cleanup
Add semicolon.
Update built files, recompile,
Andrzej spotted a serious bug
Address BLuong's feedback