Add funtionality to provide custom tick generator for quantitative scale.

Close #1058.
Fix naming.
Change tick generator signature.
Add missing d.ts files.
Change tick generator signature.
Remove non-meaningful jsdoc and rename variables.
Simplify tick generator signature.
Fix jsdoc.
Fix typesig.
Add quick test for tick generator.
Merge branch 'develop' into tick_generator

Conflicts:
	plottable-dev.d.ts
	plottable.d.ts
	plottable.js
	src/scales/quantitativeScale.ts
Modifications to Tick Generator quicktest
Merge pull request #1121 from palantir/tick_generator

Custom tick generation