Use the native stdlib by default (Py2 stdlib on Py2) for import hooks

- Also make the hooks and suspend_hooks context managers restore
  the state of sys.modules in __exit__().
More tweaks to native stdlib
Add an initial fixer to create imports like "import future.standard_library.configparser as configparser"
Disable setup of missing email package for now
Require imports for ambiguous module names to be explicit
Change urllib test to use an explicit import
Get the standard library tests passing
Mark the unbound method transfer test for super() as xfail
Reduce verbosity of some tests

Also remove xfail from test_div in past.tests.test_translation. (This still
might fail on Py3)
Fix test for intern in past/tests/test_builtins
Add (disabled) test for NumPy cast as newint
Make imports explicit for tests of email and xmlrpc
Point the urlparse tests at the backported urllib.parse lib
Move native Py2 stdlib modules to future.moves
Refer explicitly to backported future.standard_library modules
Scrub modules explicitly in a test with importing builtins
Remove empty file
Add test_buffer from test/buffer_tests and test/test_bytes

Currently tests are failing because bytes(b'...') != bytearray(b'...')
Fix comparison of bytes(b'...') with bytearray(b'...')
Fix email.parser