build: update build system to use PEP 517

[mortonne]

These changes add support for the new Python package building system introduced in PEP 517. This makes it so users can install the package using pip, which is the recommended installation method now. This version will install the build dependencies (numpy and cython) automatically, so the user doesn't have to install them separately first.

I've also included pandas and h5py as requirements, so the whole package will be usable from the standard installation. They could instead be listed as optional requirements in the setup config if you preferred.

To install using this version:

• pip install $path_to_clone - if you have a local clone
• pip install git+https://github.com/mortonne/pyedfread - install directly from GitHub (here, using my fork; if this pull request is accepted, users could use the original repo)

[gschwim]

FYI - I think this repo may be dead.