move docker test script

Dockerfile

@@ -5,4 +5,4 @@ RUN curl -sS https://getcomposer.org/installer | php
 RUN mv composer.phar /usr/local/bin/composer
 RUN chmod +x /usr/local/bin/composer
 RUN composer install
-ENTRYPOINT ["./vendor/phpunit/phpunit/phpunit"]
+ENTRYPOINT ["./vendor/phpunit/phpunit/phpunit", "--colors=always"]

README.md

@@ -47,5 +47,6 @@ $span->end(); // pass status as an optional argument
 # Testing
 To make sure the tests in this repo work as you expect, you can use the included docker test wrapper:
 
-1.)  Make sure that you have docker installed
-2.)  Execute `script/dockertest` from your bash compatible shell.  You should see the test output like so
+1.)  Make sure that you have docker installed  
+2.)  Execute `./resources/test-using-docker` from your bash compatible shell. 
+You should see the test output like so

resources/test-using-docker

@@ -0,0 +1,3 @@
+#!/bin/bash
+docker build . -t opentelemetry-php-docker-tests
+docker run -it opentelemetry-php-docker-tests