Improve instructions

[aslom]

It would be much easier if installation was one liner and required sample.yaml was included in github repo.

[aslom]

Also add something to README about troubleshooting - for example apply works but it fails ...

(base) aslom@m cloud-functions-operator (master) $ kubectl apply -f sample.yaml
function.ibmcloud.ibm.com/greetings created
(base) aslom@m cloud-functions-operator (master) $ ibmcloud wsk action invoke greetings -br
error: Unable to invoke action 'greetings': The requested resource does not exist. (code efabc39430c040b264aafbd7f24095d8)
Run 'wsk --help' for usage.

[pdettori]

I suggest we do something similar to what we have done in https://github.com/IBM/cloud-operators#installing-the-operator for a one-liner install.