added host and docstrings to resources module

[avantikalal]

• Added host as an optional argument to all model zoo related functions in grelu.resources so that users can choose which model zoo to load models from.
• Added documentation to all grelu.resources functions.

Addresses #16

[gokceneraslan]

LGTM. One small fix we can fold into this is to add anonymous="allow" to wandb.login by default, which gave us some trouble in the colab notebook. I think the default is anonymous='never', so wandb forces the users to login. With anonymous='allow' it checks if the user is already logged in, and if not it creates an anonymous credential and moves on.