update installation instructions to make build requirements clear

Author: markxnelson

site/installation.md

@@ -13,6 +13,13 @@ Note that there is a short video demonstration of the installation process avail
 
 ## Build the Docker image for the operator
 
+The following software are required to obtain and build the operator:
+
+*    Git (1.8 or later recommended)
+*    Apache Maven (3.3 or later recommended)
+*    Java Developer Kit (1.8u131 or later recommended, not 1.9)
+*    Docker 17.03.1.ce
+
 To run the operator in a Kubernetes cluster, you need to build the Docker image and then deploy it to your cluster.  The operator is built using Apache Maven, which must be installed first.  Maven may be downloaded from the [Apache Maven site](http://maven.apache.org).  The GitHub repository should be cloned locally:
 
 ```