re-adding the unicode flag to the documentation about regex

The regex lib has more possible flags than the base re module. One of these restores the python 2.x re modules unicode flag, which forces the regex lib to treat the string like Unicode. Without it, it will test the type first and evaluate it accordingly. Parsimonious tests for handling unicode via a flag already, so it is useful to restore this in the documentation.

We may consider adding support for the other flags supported by regex in the future

README.rst

@@ -258,7 +258,7 @@ Syntax Reference
 ``things+``             One or more things. This is greedy, always consuming as
                         many repetitions as it can.
 
-``~r"regex"asilmx``     Regexes have ``~`` in front and are quoted like
+``~r"regex"ilmsuxa``    Regexes have ``~`` in front and are quoted like
                         literals. Any flags_ (``asilmx``) follow the end quotes
                         as single chars. Regexes are good for representing
                         character classes (``[a-z0-9]``) and optimizing for