Improve the Documentation

[radumas]

While the API is to some degree documented in a notebook under doc/, an entity relation of the 3 tables would be helpful to newcomers + any other info you think is helpful to someone jumping into this project!

[raspyweather]

I think this is the right place to point the broken link in the main readme out

[cielf]

I think this is the right place to point the broken link in the main readme out
Could you specify which link is broken? (So the fixer doesn't have to check every link.)

[raspyweather]

sure, this one

ttc_subway_times/README.md

Lines 7 to 10 in a5828c1

	We have a Python scraper running on AWS saving predicted subway arrivals since late February 2017. We need to process this data to generate observed station arrival times for each train at each station. There was a couple month hiatus in data scraping because the database was full between August and November, but the scraper is now continuing to hum along nicely.
	We're still trying to process the predicted arrival times obtained from the API into reasonably reliable state. This work is happening in a Jupyter Notebook [Filtering Observed Arrivals.ipynb](doc/Filtering%20Observed%20Arrivals.ipynb); it is mostly in SQL, despite being in a Python notebook.

[radumas]

Thanks friends!