"install ./pkg@1.2.3" should install local module
test: express is not in mocks, use underscore instead
Check for file-ness in /-containing install args

And only *then* handle the @-ness of it

This also allows for stuff like foo/bar@./path or foo/bar@http://...
for a hyothetical future when / is allowed in package names, if that
ever happens.

Re #4666
Merge https://github.com/npm/npm

Conflicts:
	lib/cache.js
npm version bump