folders should not be returned by pexpect.which()
remove all unnecessary imports
rewrite history
Merge pull request #62 from pexpect/pull-37-try-3

folders should not be returned by pexpect.which()
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