Extending Truffle's Node class.
Added Mumbler datatypes. Created MumblerTypes class.
Added execute* methods to MumblerNode.
Removed old classes from simple interpreter.
Added node classes for literal types.
Added SymbolNode to look up variables.
Adding function calling nodes InvokeNode and DispatchNode.
Added the four special form nodes.
Added lambda special form.
Added now and println builtin nodes.
Added addition and print builtin functions.
Converted Reader class to return MumblerNode objects.
Updated Reader to return MumblerNode objects.
Using Truffle in project names instead of Graal.
Main class now starts interpretor.
Fixed some bugs.
Added more builtin nodes.
Added fibonacci implementation for Simple Langauge.