Knackpy

Fixes 79: 5xx API errors will be handled as timeouts, and therefore will retry until the `max_attempts` value is reached.

Fixes a bug in which the connection field formatter was failing when trying to `string.join()` `int` type connection identifiers.

- Fix bug in which "raw" keys were not properly evaluated when field values were empty
- Fix formatting of handle multi-select multiple choice formatting: `.format()` returns a string of comma-separated choice values

- Fix Record __repr__ to handle nonetype case

- Actually handle subfields when writing to CSV
- Add support for `record_limit` and `filters` when writing to CSV
- Add missing `App` class public methods to docs

This is first production release of Knackpy v1.0! This is a complete overhaul of knackpy. Read the complete documentation [here](https://cityofaustin.github.io/knackpy/).

Notable new features:
- file uploading
- ability to fetch data by object or view name
- smarter record formatting with support for all Knack field types
- ability to provide a custom API subdomain (e.g, for HIPAA apps)