Add simple .travis.yml file and fix running doctests with `nosetests`
Fix tests for Python3.

`imap/map` behaves differently in Python 2 and 3 when `None` is given as
the callable (first input).  Python 3 raises a TypeError, which is preferred.

`pip --use-mirrors` is deprecated.  Removed.
TravisCI: test failed doctest.
Remove "cydoctest.py" since doctests now run via nosetests.
Use `nosestests` that comes with TravisCI (don't install via pip)
Don't do `python setup.py install` in .travis.yml
Fix intentionally failing test.
TravisCI: add "pypy" just to see what happens
Remove pypy from travis
Merge branch 'master' into travis_simple

Merging manually in order to run tests in master on TravisCI
Merge pull request #13 from eriknw/travis_simple

Add basic .travis.yml