Fix inclusion of vendor directory

Also removed README.md and LICENSE from MANIFEST.in and package_data
from setup.py.

There was no reason for the readme and license to be in the manifest
template since setuptools by design doesn't extract non-package files.
(This could be circumvented by placing a duplicate file in the pync
package subdirectory)

The package_data option isn't needed so removed it.

fixes SeTeM/pync#15