DOC: make experimental functionality more visible in release notes
Merge pull request #5037 from cpcloud/exp-rls-notes

DOC: make experimental functionality more visible in release notes
CLN/ENH: add parse_dates arg and use TextReader
ENH: add tupleize_cols, thousands args;

tupleize_cols=False by default, for back compat

thousands=',' by default, because we're not parsing CSV
TST: still failing test