Add flag for turning off tests

[lkysow]

Useful in the case where users are running helm template and they don't want the test Pod submitted. When running helm install, helm won't submit the Pod, only if users manually run helm test.

Adds docs to #144, closes #144

[ishustava]

This looks good, but I think it'd be nice to add a unit test for this.

[lkysow]

This looks good, but I think it'd be nice to add a unit test for this.

Good call, I just added a test for the flag on/off rather than the contents of the Pod manifest since that unnecessary but happy to add a bit more template testing if you think it's warranted.

[ishustava]

Awesome!