Delete via reference currently requires download first

[BSVogler]

given a Patient id I want to delete it from the server. This code is required to make it work.

client.reference('Patient', str(userid)).to_resource().delete()

The code above downloads the resource first, although it is not necessary. It would be good to have

client.reference('Patient', str(userid)).delete()

instead.

[BSVogler]

Might be related with this #101

[ruscoder]

@pavlushkin please take a look, it's related to refactoring you're making for conditional operations

[ruscoder]

Will be fixed in 2.0.0 using client.delete('Patient', 'id') or client.delete('Patient/id')

[ruscoder]

Also added helpers for BaseReference to use reference.delete() and reference.patch(**kwargs) as it was requested in the issue