docker dev start: fix version check

Adapt script so that it can handle versions numbers like 1.9.0

docker_dev_start.py

@@ -25,7 +25,7 @@
 __updated__ = '2017-08-24'
 
 # Check the version of the "docker" package
-if docker.__version__ != '1.9':
+if docker.__version__.split('.') < [2]:
     print("the version of the docker package is {} instead of 1.9"
           .format(docker.__version__))
     sys.exit(1)