chore(minor style and speed optimizations to rg.py)
chore(minor style and speed optimizations to rg.py)

`loc_types` now returns a set instead of a list
`_locs_around` is easier to read
`locs_around` has fewer set/list reassignents.
Removed operator import for `_locs_around`

Closes #42

mpeterv/rgkit,RobotGame/rgkit,RobotGame/rgkit,mpeterv/rgkit