fix($http): ensure case-insens. header overriding

If user send content-type header, both content-type and default
Content-Type headers were sent. Now default header overriding is
case-insensitive.
docs(ngRepeat): fix typo
fix(Angular.js): don't crash on invalid query parameters
docs(cookbook/helloworld): display "World" if no name is entered
refactor(angular.bootstrap): rename internal function
Merge branch 'master' of https://github.com/angular/angular.js

Conflicts:
	src/Angular.js
	test/AngularSpec.js