setup.py: rename splat package + improve

This is to avoid a global package name clash with existing
splat (SpeX Prism Library Analysis Toolkit).  The source code
remains otherwise unchanged.

* change name to 'verdigris.mu-splat'
* add long_description
* add Splat.pdf
* add py_modules
* add classifiers
* add github.com URL
setup.py: import setuptool when possible

This makes it possible to run the bdist_wheel command.
setup.py: use README.rst for long_description
gitignore: add MANIFEST
setup.py: tweak description
update version to v1.4