make TT_USER > TT_ERR, remove TT_MAX
fix base64 example to parse more than the 2- and 1-byte special cases
remove comments about bugs that no longer exist
use h_in for restricted base64 digit cases
allow h_whitespace(p) to succeed on end of input if p succeeds
Merge pull request #23 from pesco/tt_user

make TT_USER > TT_ERR, remove TT_MAX
Merge pull request #24 from pesco/base64-example

Base64 example
Merge pull request #25 from pesco/fix-whitespace-end

allow h_whitespace(p) to succeed on end of input if p succeeds