Add test that compares docstrings of functions in `toolz` and `cytoolz`.

This is to improve maintainability.  If docstrings don't match, then a
convenient diff is printed.  Docstrings in `cytoolz` may have additional
lines at the beginning and end.
Add function signature to docstrings.

`embedsignature=True` compiler directive is used to automatically add
signatures to functions defined in pyx files.  Signatures were added manually
to `cdef class` extension types, and `test_embedded_sigs.py` test was added
to verify these signatures are up to date with `toolz`.
Merge branch 'docstring_test' into embedsignature
Simplified "test_docstrings.py" and "test_embedded_sigs.py".

The tests in those files shared similar, somewhat convoluted logic.  A more
functional approach is now done, which makes it more clear and more concise.
Test all cytoolz docstrings for signature at beginning followed by one blank line.

Also, don't use `dict.has_key`, because it's not in Python3.
Add tests to ensure None is safe input.  Addresses #6.

Arguments that are strongly typed Python object (like `dict`) may also be None.
Although many C API functions check for type, some don't, and passing None may
result in an uncatchable SystemError or possibly a segfault on some systems.
This actually turned out to be a very minor issue, but is one we should
continue to test for.
Merge pull request #12 from eriknw/nonesafe

Add tests to ensure None is safe input.  Addresses #6.
Merge branch 'master' into embedsignature

Conflicts:
	cytoolz/dicttoolz.pyx
	cytoolz/itertoolz.pyx
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 pull request #11 from eriknw/embedsignature

Add function signature to docstrings
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