remove python2.6 check in tests.py

There's no way that this library supports python2.6, and even if it
does, it's not a target or something worth maintaining.
split meta-testing into separate files
remove unused modules from test helpers
remove test helpers and meta testing

The meta testing code was really redundant. There are libraries and
tools already made for coverage tests.

Also, it was causing a problem with the unit testing because importing
the unittest module inside of another included module is apparently
broken. Why would that be broken?
remove a useless test
remove unused imports from tests.py
separate some of the integration tests

These tests require extra assets to complete. At the moment they
shouldn't work because the data isn't available.
remove a file that was created during a test
clean up the formatting in test_write_all_labels
move a TestAsmList test into tests/integrations/
move TestEncodedText into tests/integration/
separate more integration tests
improve the test for incbin splitting
fix a test that used Label

Label had changed since the test was first written.
fix setUpClass for a unittest.TestCase
make isolate_incbins not take a global asm

Why on earth was this using globals?
fix the test for calculate_bank

There shouldn't be any exception thrown by calculate_bank since it was
changed some time ago.
Merge branch 'better-testing' into master