Allow angle bracket as VanillaSymbol

Typing < or > in a textblock would cause a "prayer failed: no unmatched angle brackets" error.
fix hotfix for typing < and > in TextBlocks

the hotfix should be in the TextBlock code, not in VanillaSymbol

updates #145/#148
comment Ctrl-V in Firefox/Opera test case #comment #doc

comment test case with what actual situation is expected to produce that
sequence of events
test for Ctrl-V in Firefox/Opera with input event

because new versions of Firefox/Opera also fire an `input` event in
between the `paste` event and the timeouts expiring
fix #149: clear stale timeouts in textarea manager

whenever we set a timeout, the previous timeout is now obviously stale,
so clear it if possible (clearTimeout() fails silently)
fix typing < and > in RootTextBlock

http://github.com/mathquill/mathquill/pull/148#issuecomment-12587451
add semicolon to unterminated statements
fix bug w/ MathElement.postOrder arguments

MathElement.postOrder uses arguments instead of the
appropriate slice of arguments
remove some unused local variables
remove documentation of Point

Point was prematurely documented in the master branch
remove duplicate declaration of local variable
Merge pull request #155 from bsuh/master

Herp derp cosmetic fixes
fix stretched parens etc not being grayed
Merge 'master' (pre-'refactor.directions') into dev

fixes unit tests failing (#149) on dev

Conflicts:
	src/commands.js
	  master added some missing semicolons to TextBlock
	  dev moved TextBlock to text.js, w/o missing any semicolons
	src/cursor.js
	src/math.js
	  ^ all 3 of these had some conflicts due to dev being
	    directionalized, but not yet master
	src/rootelements.js
	  master fixed typing < and > in RootTextBlock by passing their
	    html into VanillaSymbol
	  dev replaced all insertNew calls with createBefore calls