Beginnings of the new lexer
New lexer appears to be working correctly
Branched for better code organization
Adapted parser for new lexer; output looks correct
Updated test.k and mandel.k to conform to current syntax
Adapted codegen to support new AST model

Also moved print.go -> main.go and added the ability to codegen &
execute the input. Still needs interactive mode and better file
handling.
Merged lexer & parser rewrite with main branch
Updated readme