Update BASE_URL

Based on this comment, I think the BASE_URL is wrong
https://www.reddit.com/r/Pavlok/comments/ozj1l0/comment/hagb1yn/?utm_source=share&utm_medium=web2x&context=3

https://github.com/Behavioral-Technology-Group/Pavlok_Node_Module/blob/master/index.js#L19