Fixes for Python 3.3 and 3.4

[takluyver]

With these fixes, depyc works on itself on Python 3.4.

• MAKE_FUNCTION now expects a name on the top of the stack, then the code object. The name appears to be redundant with the name embedded in the code object, so for now I discard it.
• The TryExcept and TryFinally AST nodes were unified into a single Try node. Added support for this.

I'm assuming that there's no need to support Python 3 versions earlier than 3.3; if there is, extra branches will be needed for that.

All the affected code is in py3op functions, so operation on Python 2 should be unaffected.