wip, better error handling, windows fixes, assume no stderr
neater looking startup for popen2 python
wrap python_header in a bunch of try-except
error checking, wip
minor edits to isequal/isequaln, clarify 2 or more args.
atan2 and new helper routine for binops
array tests for expand and int
diff: some bug fixes for diff, better performance on arrays

Add new tests.
Reformat other tests.
Better performance: pass whole matrix to sympy rather then
comp-by-comp.
helpers: add unicode and update binop_code
port ineq_helper to unicode_helper

Older code still there, remove later.