ewa and ply 2.3

[jsmullyan]

The last ewa release is incompatible with ply 2.3, because it includes
a generated parser that only works with ply 2.2. If you want to use
ply 2.3, you can delete ewa/_ruletab.py and replace it with the
version in SVN, or generate it yourself:

>>> from yacc import yacc
>>> from ewa.ruleparser import RuleParser
>>> yacc.yacc(module=RuleParser(), tabmodule="_ruletab")
^D
$ cp _ruletab.py /path/to/ewa/_ruletab.py

I think I'll bundle a version of ply with the next ewa release so that
we don't need to worry about going out of sync in future.

js