Token string output to match previous format
template Token on char type
escape newlines when printing Token payloads
more tests
template Lexeme on char type
mutable Lexeme and add copy ctor
Lexeme emits Token from string as well as regex match
test for trailing newline
Tag revert to sensible values
template Lookahead on char type
add template Tokenizer, templated on char type
test case for input with newlines
empty Lookahead once we fail to match a Lexeme