new release 1.3.1, correcting docs to work in a release agnostic way and add reference to included PostgreSQL module

Dockerfile

@@ -2,7 +2,7 @@ FROM alpine:3.10
 
 MAINTAINER PrivateBin <support@privatebin.org>
 
-ENV RELEASE   1.3
+ENV RELEASE   1.3.1
 ENV PBURL     https://github.com/PrivateBin/PrivateBin/
 ENV S6RELEASE v1.22.1.0
 ENV S6URL     https://github.com/just-containers/s6-overlay/releases/download/

README.md

@@ -9,7 +9,7 @@ This repository contains the Dockerfile and resources needed to create a docker
 Assuming you have docker successfully installed and internet access, you can fetch and run the image from the docker hub like this:
 
 ```bash
-docker run -d --restart="always" --read-only -p 8080:80 -v privatebin-data:/srv/data privatebin/nginx-fpm-alpine:1.2.1
+docker run -d --restart="always" --read-only -p 8080:80 -v privatebin-data:/srv/data privatebin/nginx-fpm-alpine
 ```
 
 The parameters in detail:
@@ -27,10 +27,10 @@ The parameters in detail:
 In case you want to use a customized [conf.php](https://github.com/PrivateBin/PrivateBin/blob/master/cfg/conf.sample.php) file, for example one that has file uploads enabled or that uses a different template, add the file as a second volume:
 
 ```bash
-docker run -d --restart="always" --read-only -p 8080:80 -v conf.php:/srv/cfg/conf.php:ro -v privatebin-data:/srv/data privatebin/nginx-fpm-alpine:1.2.1
+docker run -d --restart="always" --read-only -p 8080:80 -v conf.php:/srv/cfg/conf.php:ro -v privatebin-data:/srv/data privatebin/nginx-fpm-alpine
 ```
 
-Note: The `Filesystem` data storage is supported out of the box. The image includes PDO modules for MySQL and SQLite, required for the `Database` one, but you still need to keep the /srv/data persisted for the server salt and the traffic limiter.
+Note: The `Filesystem` data storage is supported out of the box. The image includes PDO modules for MySQL, PostgreSQL and SQLite, required for the `Database` one, but you still need to keep the /srv/data persisted for the server salt and the traffic limiter.
 
 ### Timezone settings