Added global property "prompt" which allows the user to set their own prompt, through a function or hardcoded string.
Added command and utility for executing external files (require won't do because it assumes he file is a module and wraps it).
App now uses this to execute scripts on startup: both ~/.nsh.js and ./.nsh.js are executed, if they exist, in that order.
Included sample local startup file.
Added information for the new features on the readme.