Include Tests

[ryanlevy]

Create a set of tests so we know things work. Also added the formatter

Current things to test:

• [x] Function evaluations
• [x] Tanh evaluation
• [x] Adding functions

Should close #4

[JoeyT1994]

Looks great! Thanks. Can you also add a couple of tests that try out a different geometry? I.e. a few loopy networks/ other types of trees? (For functions with bond dimension > 1)

[ryanlevy]

Did some renaming and added an alias, will add some geometry next (also maybe need to address the CI)