Update header comment

Update brief description, copyright notice, maintainer, tags, and
commentary.
Rename library

Rename the library from python-pylint to run-pylint, and update variable
and function names accordingly.
Update documentation

Update docstrings and add a README.
Make run-pylint-options a constant

Change `run-pylint-options' from a defcustom to a defconst, because
changing the pre-defined options may break the compilation-mode parsing,
and the user may use a Pylint config file anyway.