Rename postgresql image to postgres

Use postgres instead of postgresql for the image name to align with the
Docker official library upstream.

Signed-off-by: George T Kramer <george.t.kramer@intel.com>

.travis.yml

@@ -11,7 +11,7 @@ env:
   - DOCKERFILE_DIR=mariadb
   - DOCKERFILE_DIR=stacks/dlrs/oss
   - DOCKERFILE_DIR=stacks/dlrs/mkl
-  - DOCKERFILE_DIR=postgresql
+  - DOCKERFILE_DIR=postgres
 
 script:
   - cd $DOCKERFILE_DIR

postgres/README.md

@@ -5,19 +5,19 @@ This provides a Clear Linux* PostgreSQL instance.
 Build
 -----
 ```
-docker build -t clearlinux/postgresql .
+docker build -t clearlinux/postgres .
 ```
 
 Or just pull it from Dockerhub
 ---------------------------
 ```
-docker pull clearlinux/postgresql
+docker pull clearlinux/postgres
 ```
 
 Start PostgreSQL Container
 -----------------------
 ```
-docker run -p 5432:5432 -e POSTGRES_PASSWORD=secret -d clearlinux/postgresql
+docker run -p 5432:5432 -e POSTGRES_PASSWORD=secret -d clearlinux/postgres
 ```
 
 Environment Variables