Fixes the reading of dependencies that have spaces in their subspecs' name from Lockfiles

Closes https://github.com/CocoaPods/CocoaPods/issues/2850.
Should've been done with https://github.com/CocoaPods/Core/pull/179.

See http://regexr.com/39uen.
> I think the change just has to do with greediness. :shrugs: This is why I added tests

And if the change was only about greediness, why not add the corresponding flag, or add the greediness inverter `?` after all the `*` to change them to `*?`? That should have done the trick too, without the need to change group capturing and all the RegExp form?

Still don't understand what the RegExp is supposed to do. I mean I understand it literally but I'm not sure it matches what is expected in all cases, depending on what form a string dependency may be.