Add HAS_POSITIVE_NUMERIC_VALUE to DOMProperty and normalize behavior of null values

Uniformly remove null values, rather than sometimes set/remove, could potentially assign 'null' or 'undefined'
Fix ReactDOMTextarea missing "rows" and "cols" attribute, incorrect "size" property
corrections
Clean trailing space and lint
Improving never seen error message

Removing repeating "support it" and fixing camelCase method name
match -> test

Using RegExp method `test` because this is what is wanted
Add loop property
Fix SelectEventPlugin

mouseup was not fired when context menu showed, so select events stopped being fired.
URL -> url
test case for ReactTextComponent rootID escaping
fixes ReactTextComponent rootID unescapedness
JSXTransformer now supports IE8

Conflicts:
	package.json
utils.* is now used everywhere
Don't call utils.traverse in transform

Accidental change we missed in review of #495.