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
Account for NaN and undefined values on Plot.Line and Plot.Area

Makes use of d3's defined() option on its Line and Area
generators to skip NaN and undefined values.

Adjusted Plot.Line and Plot.Area unit tests to create a new Plot
for each test, reducing cross-dependency between tests.
Enable rotation of CategoryAxis tick labels by angle.
Right now only 0 (horizontal), 90 (right), and -90 (left) are supported.
This feature is not well supported and will only work for short strings.

Related to #504
Satisfy the linter
Add total animation duration limit endpoint to control the time for whole iterative delay animation.

Close #1117.
Fix bizzare bug in travis
Improve tests, pass index to defined().

Had to modify d3.d.ts; will submit PR to DefinitelyTyped.
Fix linting errors.
Add NaN values to Line and Area animation quicktests.
Update jsdoc and currect null check.
Address Brandon's concerns. I expect it will mysteriously fail in Travis
Clean concise code
Renaming to privide better understanding for knobs' priority.
Making array / map differentiation