Merge pull request #58 from ashleyh/master

add stubs-auto directory & fix #34
cgen: Start work on classes
Add C code generation test case runner

These perform checks on the generated C code.

Also add a single trivial test case.

Closes #68.
cgen: Support simple method calls

Also generate vtable. Everything is still very much work in progress.
Vtable are not very efficient: they have an extra level of indirection.
Improve code formatting
cgen: Support attribute access

Also include space for slots when allocating instances.

Note: Slots are still not initialized!
cgen: Add test case
icode: Initialize non-int globals to None

Closes #71.
icode: Use special opcode for None expressions

Also add cgen None expression test case.
icode: Add test case for value expr conditions
cgen: Support simple value expr conditions

These only check against None; 0 is not recognized as False.

Close #70.
Minor optimization
icode: Fix classes with __init__ args and fields
cgen: Support __init__ methods

Close #46.
Disallow __init__ in interfaces: fixes #52