Unable to get off the ground following the "quick start" section

I have tried to use kafka both building form source via gradle as well as
un tgz-ing the tarball. Either way, none of the scripts work in the way
described in the Quick Start section.

Following is an example :

6:15:40/kafka:91 $bin/zookeeper-server-start.sh config/zookeeper.properties
Exception in thread "main" java.lang.NoClassDefFoundError:
org/apache/zookeeper/server/quorum/QuorumPeerMain
Caused by: java.lang.ClassNotFoundException:
org.apache.zookeeper.server.quorum.QuorumPeerMain
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)