Allow Renderer's DataSource to be Changed
Allow nonunique x/y values on BarRenderer/HorizontalBarRenderer

Previously data binding was keyed on the x-value, so if bars shared
the same x-value only the first would be drawn (The same thing for
shared y-values on HorizontalBarRenderer).

Close #435.
Update built files
Add tests to ensure one bar per data point.
Merge remote-tracking branch 'origin/master'

Conflicts:
	src/core/renderer.ts
made bar renderers default blue
close #441
Update built files
changed to ES6 syntax
merged with master (with conflicts)
fixed conflicts
fix axis postitioning bug (issue #420)

When an axis position was changed to "top" or "bottom", the axis gets
longer. But when it gets changed back to "middle", it stays long.  The
same applies to horizontal axes.

This diff makes it get shorter again.
Merge branch 'master' into axis-position
Merge pull request #450 from palantir/441-default-steelblue

made bar renderers default blue
orient quicktests
Axis._DEFAULT_TICK_SIZE = 6
Merge branch 'master' into axis-position
Update built files
orient transformation resets
Merge remote-tracking branch 'origin/master'
Update built files