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.
Merge pull request #1159 from palantir/stackedArea0

[Hotfix --> master] - Stacked Area with 0 valued datum uses the positive offset value
Merge pull request #1165 from palantir/emptyDatasetFailure

[Hotfix --> master] - [StackedArea] - Projection logic allows for empty datasets
Fix typesig.
Release version 0.32.1
Covers 0-length dataArray case
Test renames
Modifying test message
Add quick test for tick generator.
Change plottable.d.ts to include protected methods.
Remove plottable-dev.d.ts.
Remove copy-dev-defs task.
Merge pull request #1179 from palantir/full-definitions

Change plottable.d.ts to include protected methods.
Remove API changes warning from README