remove duplicated timestamp

Makefile

@@ -125,7 +125,7 @@ README_HEAD = `cat ./_README.md | sed -e 's/%CONTAINERS_LIST%.*//g'`
 README_TAIL = `cat ./_README.md | sed -e '1,/%CONTAINERS_LIST%/d'`
 
 update_readme:
-	@echo "$(README_HEAD)\n - $(TOOLSET) $(README_TAIL)" | sed -e "s/%LAST_UPDATE%/\n_Last update: `date`_ \n/g" > README.md
+	@echo "$(README_HEAD)\n - $(TOOLSET) $(README_TAIL)" | sed -e "s/%LAST_UPDATE%/\n_Last update: `date`_ \n/" > README.md
 
 delete_dangling_images:
 	@echo "Removing dangling images"

README.md

 [![pipeline status](https://git.unl.edu/unl-its/docker-ci/badges/develop/pipeline.svg)](https://git.unl.edu/unl-its/docker-ci/commits/develop)
 
 # Docker-ci
-Containers used on CI
 
-## Building Images
+## Containers usefull in CI process
+
+### Building Images
+
 To build these images, clone this repository onto a machine with docker and make installed. Run `make` and all of the images will be built and installed as local docker images.  
+This file is automatically updated after execute `git commit` based on the content of file `_README.md` 
+
+### Tools available:
+
+
+
+
+_Last update: Thu May 30 15:37:41 CDT 2019_ 
+
+ - its-registry.unl.edu/unl-its/docker-ci/detect-secrets:latest
+ - its-registry.unl.edu/unl-its/docker-ci/magento2-unit-test:latest
+ - its-registry.unl.edu/unl-its/docker-ci/magento2-xml-lint:latest
+ - its-registry.unl.edu/unl-its/docker-ci/php-lint:5.6
+ - its-registry.unl.edu/unl-its/docker-ci/php-lint:7.0
+ - its-registry.unl.edu/unl-its/docker-ci/php-lint:7.1
+ - its-registry.unl.edu/unl-its/docker-ci/php-lint:7.2
+ - its-registry.unl.edu/unl-its/docker-ci/php-lint:latest
+ - its-registry.unl.edu/unl-its/docker-ci/php-unit-test:5.6
+ - its-registry.unl.edu/unl-its/docker-ci/php-unit-test:7.1
+ - its-registry.unl.edu/unl-its/docker-ci/secrets-detection:latest
+ - its-registry.unl.edu/unl-its/docker-ci/static-code-analysis:latest
+ - its-registry.unl.edu/unl-its/docker-ci/static-code-analysis:php
+ - its-registry.unl.edu/unl-its/docker-ci/static-code-analysis:python 
+
+_Last update: Thu May 30 15:37:41 CDT 2019_ 
+