Merge pull request #2 from docker/badge

Reopening branch because the badge didn't display

README.md

@@ -3,4 +3,8 @@ Internet2 managed CentOS 7 base image
 
 ## status
 
-[![Build Status](http://jenkins.internet2.jimvanfleet.com/buildStatus/icon?job=docker/base/master)](http://jenkins.internet2.jimvanfleet.com/job/docker/job/base/job/master/)
+![Build Status](http://jenkins.internet2.jimvanfleet.com/buildStatus/icon?job=docker/base/master)](http://jenkins.internet2.jimvanfleet.com/job/docker/job/base/job/master/)
+
+## purpose
+
+This container allows I2/TIER to insulate itself against upstream changes from CentOS managed images that may be unwanted.  It can also be used to trigger global changes (e.g. a new InCommon.crt) when appropriate.