[fixed] The argument to Form.extend() is no longer mutated

Quick patch to ahallow-copy prototypeProps, this will need to be fixed in Concur
v0.9.1

The object given to Form.extend() is no longer mutated.
Merge remote-tracking branch 'origin/0.9' into react

Conflicts:
	CHANGES.rst
	README.rst
	lib/forms.js
	package.json