initial work
some more functionality
added requestedSpace
added tickDensity
removed some unnecessary code
Merge branch 'master' into date-axis

Conflicts:
	quicktests/date-test.html
removed nTicks from timeAxis
Merge branch 'master' into date-axis
removed tickDensity, will move into scales at some point
Merge branch '517-number-axis' into date-axis

Conflicts:
	plottable.d.ts
	plottable.js
	src/reference.ts
added dateFormatters (but with a few warnings, will fix this later)
fixed warnings for dateFormatter
separated out time scale so now it directly descends from scale rather than quantitive scale
a few cosmetic changes
added support for specifying ticks by intervals
minor style changes
Merge branch 'master' into date-axis

Conflicts:
	plottable.d.ts
	plottable.js
	src/components/baseAxis.ts
	src/reference.ts
reverted timescales back to descend from quantitive scales (so they will play will with domainers for now)
changed timeAxis to match changes in baseAxis
updated some comments