Adding test for missing values
Accounts for missing values (mainly for stacked bar)
Massive code cleanup

Using maps instead of arrays for performance
Further clearning
Adding quicktests
Better quicktest html title
Updating d3.d.ts to reflect change in DefinitelyTyped PR
Clean concise code
Making array / map differentiation
Adding return typing
Removing newline
Factoring out accessor logic to function
Better test message
Merge branch 'develop' into missingStackedBar

Conflicts:
	plottable-dev.d.ts
	plottable.d.ts
	plottable.js
Sticking with maps
Remove newline
Refactor code
Merge branch 'missingStackedBar' into develop

Conflicts:
	plottable-dev.d.ts
	plottable.d.ts
	src/core/interfaces.ts