Updated all dependencies including Firebase

[patpatchpatrick]

I updated all of the pod dependencies, including Firebase, so that the most recent versions of Firebase/Firestore can be used. I tested everything in my project and it seems to be working fine.

[AlexanderMarchant]

Please be aware:

This update introduces a dependency on the 'GeoPoint' class to be mapped onto your swift object. If you do not use the GeoPoint mapping on your object, other features - such as locating documents within a radius - will not work correctly.

Previous possible mapping:
var l: [Double]

New required mapping:
var l: GeoPoint

Not a biggie, but GeoPoint does not conform to codable, therefore, I needed to create my own codable implementation and play around with the JSON before attempting to decode my object containing the GeoPoint.

My workaround being I removed the GeoPoint JSON from the JSON object and manually instantiated a GeoPoint object then assigned it to the objects field after decoding the other JSON.

Otherwise, thanks for this pull request.