Icon radius now scales with text height

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

Close #767.
Resetting to original plottable.css file
assert.isTrue -> assert.operator, adding fail msg
Icons are too big -> small where appropriate
Removing unused test var
Merge branch 'master' of github.com:palantir/plottable into 767-iconRadiusChanges

Conflicts:
	plottable.js
	test/tests.js
Merge pull request #777 from palantir/767-iconRadiusChanges

767 icon radius changes