I installed this plugin using the Jenkins manage plugins section. My initial error was
FATAL: Unable to initialize command context. because I had not installed wildfly-cli 8.2.1.Final
This file was difficult find and also find the location for it to be installed. It would helpful if the instruction assisted this process. Eventually I found that the WEB-INF/lib dir is actually in two locations, one is in the /var/cache/jenkins/war dir and the others is in jenkins.war in /usr/share/jenkins. The .war must get expanded to /var/cache on regular basis so the files will need to be in both places.

I then had succession of
FATAL: org/wildfly/security/manager/WildFlySecurityManagerjava.lang.NoClassDefFoundError:
Caused by: java.lang.ClassNotFoundException. for a missing class
Every time I would find the required jar containing the missing class and install in the /var/cache and restart.

Eventually I created a blank maven project with org.wildlfy wildlfy-cli 8.2.1.Final as the only dependency and created a war file and then copied all the jars (19 of them) in the war file to the Jenkins WEB-INF/lib dir. and restarted.

Only after I did this did the the wildfly deployer pugin successfully deploy my war file to my wildfly server.

I have now successfully deployed to both wildfly 8.1.0 and 10.0.0

This issue may have only been with my installation of Jenkins as it was prebuilt Turnkey Linux virtual machine and I write this so that others who have similar issues may be able solve them easier than I did

Graham