Define binary_traits locally

Rename functions.

Fix test to actually test the right array-match.

Attempt to move doc deploy to GitHub actions.

Directly report python type in pybind11 type caster.

It looks to me like type_descr is only supposed to be used for regular
wrapped types, not custom type casters of the sort we have here.
And happily we don't need to use its magic to look up the right Python
type from a compete (i.e. template-instantiated) C++ type, because we
know all ndarray type casters map to "numpy.ndarray" regardless of
their template parameters.

cmake: add test dependencies

Building the tests requires first building the header files.

Hide Pybind11Helper symbols when pybind11 hides its symbols.

Update readme, revert non-portable pybind11 2.1 suffix fix

Remove SWIG support, add compatibility with Eigen 3.3

Update travis doc directory for deploy.