add four small and consise elisp library

The four libraries are: 
- ht: The missing hash table utility library for Emacs.
- loop: friendly imperative loop structures for Emacs lisp.
- mustache: A mustache templating library for Emacs.
- with-namespace: interoperable elisp namespaces.

All libraries are from https://github.com/Wilfred. 

These libraries are small but useful, and the code are concise and tiny.