js/README.txt instructions to run node server

I am a very lazy person and would have loved to get some basic
instructions to easily start the node server (ie without having to
browse the wiki).

Added in the instructions to create a localsettings.js and how to start
the server.  Point to the extensive wiki doc.

Change-Id: If0d2091eff2cfdf6b09ff07c415774141d4b5c50
Merge "js/README.txt instructions to run node server"