persistent-postgresql-2.1.3: ChangeLog.md

## 2.1.3

* Added a `Show` instance for `PostgresConf`.
* `createPostgresqlPoolModified` added, see [relevant mailing list discussion](https://groups.google.com/d/msg/yesodweb/qUXrEN_swEo/O0pFwqwQIdcJ)

## 2.1.2.1

Documentation typo fix

## 2.1.1

Added `FromJSON` instance for `PostgresConf`.