Clarify dependency "story" and installation procedure

At a glance, it's quite confusing currently how/what one is supposed to install in the environment to make the code in this repo work. Let's clarify that "story". Some items to fix:

• It seems reasonable for a user to expect that installing climsim_utils (via pip install .) should give them everything they need. Currently, each of those directories has a requirements-lock.txt which @jerrylin96 has indicated is for development purposes (as a reference of a known working environment). Once development on those notebooks is complete (i.e., #21 is closed), let's try to get those notebooks to run based on only dependencies in setup.py.
• The environment.yml in the repo root is actually just for the website. That's super confusing 😄 . Edit: Done in #30.
• Each of the baseline_models has it's own env/. That's presumably desirable, as we would not expect the models to run with the same env as the preprocessing/evaluation code. Perhaps we can just noted in some way in the README (if that is not already done).

Review setup.py, the per-directory requirements-lock.txt files, the root environment.yml, each baseline_models/env/, and the README, noting that #30 already addressed the root environment naming. Start by checking the remaining dependency and notebook concerns after #21; done means the installation story clearly distinguishes user, notebook, website, and baseline-model environments and the notebooks run from the documented dependencies.