fix(guide) broken title overflow in navlist
fix($http): allow empty responses to be cached

Closes #3809
feat($parse): support unicode identifier names

Support unicode identifier names as defined in Section 7.6 Identifier Names
and Identifiers, ECMAScript Language Specification
(http://www.ecma-international.org/ecma-262/5.1/#sec-7.6),
except for unicode escape sequences which is hard to implement
without changing too much existing code.

The overhead of this feature is about 4k bytes of minified code
(2.3k minified & gzipped).

Closes #3847