Remove CHANGELOG

For such a small project I would like to rely on the git log and
git branching.
Fix project name and dependencies in Modulefile
Put nodejs declaration at the top of dependencies
Remove python package from dependencies

The nodejs package already ensures that the python package is installed.
Thus, the second declaration of the python package lead to an error.
Require etherpad::setup for etherpad-settings
Add etherpad_sources variable to setup class