Tap-pendo

* Add optional sync for anonymous Visitors

* Fixed query params for `track_events` [30](https://github.com/singer-io/tap-pendo/pull/30)

* Fix issue with substreams of visitors due to new pattern using a generator rather than a list [29](https://github.com/singer-io/tap-pendo/pull/28)

* Stream `visitors` and `events` aggregation responses via ijson [28](https://github.com/singer-io/tap-pendo/pull/28)

* Fix for discovering all custom fields in `visitors` and `accounts` [27](https://github.com/singer-io/tap-pendo/pull/27)
* Add boolean type handling to custom field discovery
* When matching custom field types, any unknown type will raise an exception where the error occurred, rather than generating an invalid schema

* Allow for Discovery to succeed when no custom metadata is found [22](https://github.com/singer-io/tap-pendo/pull/22)