replace assert(_size == rhs.size()) with exceptions

also fix the depends in setup.py
add a script that will start the pyro jobs and workers

for parallel basinhopping and connect jobs.

The only information needed about the system is in the System Class.
The system class is obtained from a function create_system() which is
imported from a file or module passed to the script
add flag `overwrite=True` to database.add_property

BaseSystem checks for params.database.overwrite_properties
change default quench tolerance to 1e-5
update to xy_model
updates to parallel_pele.py script