Tap-pendo

* Add the the custom pagination support for the Visitors stream [126](https://github.com/singer-io/tap-pendo/pull/129)

* Fix infinite loop issue [126](https://github.com/singer-io/tap-pendo/pull/126)

* Update key properties for streams, fixes issue [34](https://github.com/singer-io/tap-pendo/issues/34) with missing records [#88](https://github.com/singer-io/tap-pendo/pull/88)
* Add support for app_id selection [94](https://github.com/singer-io/tap-pendo/pull/94)

* Update the lookback window validation to use typecasting using `int()` function instead of `isdigit()` [93](https://github.com/singer-io/tap-pendo/pull/93)

* Fix the type error in the accounts stream records that resulted from comparing a none value. [122](https://github.com/singer-io/tap-pendo/pull/122)

* Fix connection reset, request timeout and memory overflow issues [116](https://github.com/singer-io/tap-pendo/pull/116)
* Refactor child stream methods
* Implement logic to increase the request timeout duration during retry attempt [118](https://github.com/singer-io/tap-pendo/pull/118)
* Reduce backoff time