Feat/api changes

A number of API changes that were discussed with @JeffSpies 

- All modules live outside of the mfr core package
- Registry is now a list instead a dictionary
- mfr.register_filehandler only takes a handler class (no more names)
- `mfr.collect_static` will use a filehandler's module name as the folder name within the base static folder, e.g. `mfr_code/static/style.css` is collected to `/path/to/static/mfr_code/style.css`
- Module organization changes: see README.rst and CONTRIBUTING.rst for documented examples; in short, FileHandlers are moved to mfr_formatname/__init__.py and are always named `Handler`
- Module-level configuration: See mfr_code_pygments for a simple example of this

Please review: @JeffSpies @alexschiller @jmcarp