Python-airtable

* **Breaking**: Drop Api config from ENV variable - use `api_key` arg instead
* **Breaking**: Drop Python 2 / IronPython Support
* Feature: On HTTP Errors, Raise Original Exception, but with Helpful Errors added
* Fix: 86 formulas with string values

* Removed: `mirror()` method.
* Feature: Configurable request timeout

* Fixed: Python 2 compatibility issues
* Start CI testing on all supported Python versions
* **Breaking**: Drop implicit support for Python 3.4, officially support 3.7 and 3.8.

* Fixed: Rewrote tests
* Fixed: Improve CI and deployment

* Fixed: Add sdist and universal for 2.7 dist
* Fixed: Long dist set to markdown

* Feature: Merged PR17 - Added typecast to update, update_by_field, replace, replace_by_field