If an expression starts or ends with a bracket and only contains a single
delimiter, don't wrap it in additional optional parentheses. We can use the
brackets for the split.
Fixes#177Fixes#193
* Normalize string quotes
Convert single-quoted strings to double-quoted. Convert triple single-quoted strings to triple double-quoted. Do not touch any strings where conversion would increase the number of backslashes.
Fixes#51.
* reformat Black itself
