feat: Add README

README.md

@@ -1 +1,19 @@
-# docker-postgresql-client
+# Postgresql Client
+
+This client is compatible with the official postgresql image, which means that it uses the environment variables provided by the image.
+
+## Usage
+
+### Start a postgres database
+
+```
+docker run -e POSTGRES_USER=user -e POSTGRES_PASSWORD=pwd -d --name=pg_container postgres:9.5
+```
+
+### Use psql or pg_dump command
+
+```
+docker run --rm --link pg_container:db kalumkalac/postgresql-client:9.5 psql -c 'create database foo'
+docker run --rm --link pg_container:db -v /tmp/foo:/dump kalumkalac/postgresql-client:9.5 pg_dump foo -f /dump/dump_foo.sql
+```
+