Move tests up to 'tests' directory

for access to the assertEqualData() function
Extracted out get_interactions() functions
Extracted out psi_delta_theta()
Renamed obfuscated 'Delta' variable

oie
Renamed variable to 'scale_interaction_distance'

‘scale_interaction’ was used as a flag for enabled/disabled.. though
not used.
Simplified gx_final and gy_final initialization
Added zli.channel_interaction config
Renamed variable to 'scale_deltas'
Deal initialization
Minor refactoring for readability
Renamed newgx() and newgy() as just gx() and gy()
Minor formatting