Rough out sexpr interface and data structures
Add sexpr_parser struct for better errors
Add character stream functions to sexpr_parser
Add SEXPR_OPEN and SEXPR_CLOSE constructors
Fix error printing SEXPR_OPEN outputs ()
sexpr parses open and close parens
Remove user specific lines from .gitignore
Handle () as nil
Add EOF handling to sexpr_parser
Make sure token buffer is large enough in sexpr
Parse sexpr symbols
Parse strings
Parse numbers
Correct token position accounting
Cleanup and intgerate streaming parser
Print Done after all tests complete