change directory structure to make python package conventional
add setup.py file to specify deps
guide users to use the installed `usc-run` command
associated changes to other scripts
make scripts installable when package is installed
add a symlink for congress/run.py to run for backwards compat
remove redundant requirements file
There is no longer a separate amendments scraper. Amendments are saved as a part of importing bills. Amendments to treaties are no longer available.
some of this work was done by @crdunwel