have callbacks for dragstart, drag, and dragend
updated compiled files
Merge branch 'master' into dragevents

Conflicts:
	plottable.d.ts
give a type to `getPixelData()`
line up dragevent functions
update build file
alignment
simplify drag callback API into `upperLeft` and `lowerRight` corners
typo
`ondrag` and `ondragend` callbacks get `startLocation` and `endLocation` arguments
change `origin` in `dragstart` callback to `startLocation` for consistency
update drag callback docs
make drag callback functions act like getters/setters
Merge branch 'master' into dragevents

Conflicts:
	plottable.d.ts
	plottable.js
	test/tests.js
handle getter cases
check `arguments` not for `null`
check for `undefined`
use `Point` interface. get rid of `ICoord`
Merge branch 'master' into dragevents

Conflicts:
	plottable.d.ts
	plottable.js
	test/tests.js
update test descriptions