<WIP> Add docs build & update documentation

[lwasser]

This is a DRAFT start of rebuilding the docs.

• cleanup make build and ensure api docs are correctly building
• fix envt file / requirements file to ensure all are working
• fix TOC to ensure docs are easy to follow

CI

• setup sphinx build and push to gh pages

• squash commits and cleanup PR.

i'm doing some cleanup as i go of bad links, unused imports, etc.

Documentation Preview Here

http://www.leahwasser.com/stravalib/index.html

The final url of documentation will be: stravalib.github.io/ when this is merged i'll pull down my demo in my fork.

[lwasser]

NOTE: i will want to also remove the old API reference section. then i will make the model module nice and easy to read like the client module

finally look into tests. i just need to ensure nothing is getting broken - it shouldn't but i am cleaning up docstrings.

[lwasser]

let's test deployment now. this should deploy to gh pages if all goes well. if this works then i can do another round of cleanup, remove the old api reference pages and get the PR going. i will submit a draft now just for a start.