Clean up type-checking in builtin functions to match Python.
Add missing nb$add and nb$inplace_add methods to list, tuple, and string objects.
Call nb$add methods of sequence types when using a + operator.
Make sum handle non-number objects and throw errors like Python.
Add missing nb$multiply and nb$inplace_multiply methods to list, tuple, and string objects.
Call nb$multiply methods of sequence types when using a * operator.
Test case to check user-defined operator overloading methods.
Fix builtin pow function to properly handle nmber and lng objects.
Avoid spurious failures of t422.py.  Could it really be that different coprocessors will occasionally cause this test to fail even on the same machine?
Modify the urllib from web cat's branch so that it works with a simple synchronous xmlhttprequest object.
Merge branch 'master' of github.com:rixner/skulpt into rixner-master
Merge branch 'master' of https://github.com/bnmnetp/skulpt