Add in Dispatchers.

Dispatchers are essentially a higher-order proxy for event listeners.
They namespace event registration, so multiple dispatchers can listen
for the same event on the same element.

This is part of the setup for better Interactions in the future.
Rather than create ad-hoc listening structures in each Interaction,
in the future Interactions should use Dispatchers to listen for
events and respond accordingly.

Currently there is only the base Dispatcher and Mouse Dispatcher, but
more will be added in the future.
When there is insufficeint space to fit text, don't write any text at all

This should lead to cleaner failures when there's insufficient space.
Add unit test, commit built files
Merge branch 'master' into add-dispatchers
renamed renderer -> plot in css
cicle-plot => scatter-plot
add more tests
Merge branch 'master' into better-text-failure

Conflicts:
	plottable.js
clearbox working
clearbox working
Merge branch 'master' into add-dispatchers

Conflicts:
	test/tests.js
creating a Log results in a warning

Since Log is deprecated in favor of ModifiedLog.
onload populate dropdown with branches from git
fix typo
work on select_bars
Icon radius now scales with text height

Minor adjustment to positioning algorithm of Util.Text.writeLineHorizontally.

Close #767.
Resetting to original plottable.css file
ck commit
Merge branch 'master' into css-plot

Conflicts:
	plottable.js
730 -Clear html in label's textContainer on render

Closes #730.