Clarify warning messages
Add make clean
Edit config descriptions
Increase threshold for Lazy Load
Edit comments
Remove Ruby dependency
Remove Node.js dependency
Revert "Remove Node.js dependency"

This reverts commit 32117ec8cf29e7d7e4bcbfd610b8aeebeb65ec75.

It turns out that it is not an easy task. Python-CoffeeScript
depends on PyExecJS which depends on other runtimes including
PyV8, Node.js, Apple JavaScriptCore, Mozilla SpyderMonkey, and
Microsoft Windows Script Host (JScript) among which PyV8 is the
only Python runtime (even though it is a just wrapper).
However I cannot install PyV8 with 'pip install pyv8' since
it always stalls whenever it tries to checkout the revision
205936 of something called icu. I feel it is too early to
get rid of Node.js right now.