Move (/remove) platform_tests folder which doesn't contain real tests
Rename platform checks so py.test doesn't try to run them
Don't rely on environment variable set in test.env
Fix imports in tests for Python 3

Closes gh-59
Use py.test on Travis
Update DEVELOPERS file
Remove old test runner machinery
Remove ancient script for testing on Sourceforge compile farm (long since gone)
Remove 'make test' target
Don't try to measure coverage in some Python subprocesses
Skip performance tests on PyPy
Ignore coverage env var if not set
Don't install into virtualenv in Travis - test local copy
Use no_coverage_env() in some more tests
Allow subprocess tests to import pexpect
Merge pull request #63 from takluyver/use-pytest

Use py.test for tests