Add long/latitude, fxn for nearest bike depot.

Add:
	py/citi_bike.py
		-add function that intakes a longitude and latitude, and returns
		the address of the nearest bike depot.

	py/utils.py
		-add function to return all Mongo city_bike collection's
		documents.
Mod:
	py/citi_bike.py
		-bike depot documents sent to Mongo now contain longitude and latitude,
		in addition to an address.