Shored up the evaluate package by splitting functionality. Changes:
	FileInterpreter: Refactored out s-expression parsing.
	Reader: Deleted this class - it was empty.
	Interpreter: Renamed version of FileInterpreter to clarify role.
	Function: Removed stubbed out method.
	InterpreterTest: Conformed test to new interpreter structure.
	ExpressionParser: Contains s-expression parsing code.
	REPL: Allows for interactive code execution.