Change key naming convention of hashes that we pass to head.js() function.

At the moment we concatenate key so it becomes unreadable for big number of duplications. In one of the projects I am working, I had like 4 classes called "base" in different namespaces. That resulted in keys like:
- base
- base_base
- base_base_base_base
- base_base_base_base_base_base_base_base

Note that it grows exponentially ;)

This commit would generate:
- base
- base1
- base2
- base3