restore py2 functionality
Use py2/py3 compatible generator syntax

In py2, generators have gen.next() methods.  In py3, it's gen.__next__().  Using next(gen) works in both versions.
Refactoring to add pop_block method

We're not convinced this is a good refactoring - does it make the line self.pop_block() in the middle of the frame handling in the main loop confusing?
Towards correct block handling

This commit is fairly messy.  The core idea is to add the distinction between SETUP_EXCEPT and EXCEPT_HANDLER blocks in py3 while leaving the py2 behavior unchanged.  There are also changes to the main loop related to the way WITH is handled, which aren't fully implemented yet.
Eliminate 'with' block in py3

There's no more 'with' block in py3.  We also need to change the handling of END_FINALLY.
Fix normalizing exception

Fixes test_raise_exception_class with @jvns
Add test of `raise FooError from BarError`

This is new syntax in python3.  The failure of this test demonstrates that the RAISE_VARARGS is improperly implemented for py3.
Implement raise FooException from BarException, but ...

... break some other tests along the way.
comments
refactor out py3 behavior from py2 method
refactor do_raise slightly
more verbose logging of stack
State with five failing tests in Py3

FAIL: test_finally_while_throwing (tests.test_exceptions.TestExceptions)
FAIL: test_reraise_explicit_exception (tests.test_exceptions.TestExceptions)
FAIL: test_raise_in_context_manager (tests.test_with.TestWithStatement)
FAIL: test_raise_in_with (tests.test_with.TestWithStatement)
FAIL: test_suppressed_raise_in_context_manager (tests.test_with.TestWithStatement)
comments and logging
nope
Down to one test failure

FAIL: test_suppressed_raise_in_context_manager (tests.test_with.TestWithStatement)
FAILED (failures=1)
PASS ALL THE TESTS

(byterun_env)byterun [assorted-fixes $%] ⚲ tox
GLOB sdist-make: /Users/afk/Dropbox/python/byterun_env/byterun/setup.py
py27 inst-nodeps: /Users/afk/Dropbox/python/byterun_env/byterun/.tox/dist/Byterun-1.0.zip
py27 runtests: commands[0] | nosetests
.....................................................................
----------------------------------------------------------------------
Ran 69 tests in 1.735s

OK
py33 inst-nodeps: /Users/afk/Dropbox/python/byterun_env/byterun/.tox/dist/Byterun-1.0.zip
py33 runtests: commands[0] | nosetests
....................................................................
----------------------------------------------------------------------
Ran 68 tests in 1.618s

OK
________________________________________________________________________________ summary ________________________________________________________________________________
  py27: commands succeeded
  py33: commands succeeded
  congratulations :)
Clean up comments & logging
Merge branch 'assorted-fixes'

Conflicts:
	byterun/pyvm2.py