Update the README for testing

[ajmas]

Having recently made changes to for #19, I was unable to establish the right testing environment.

The docs indicate:

The default test will run through basic CRUD functions, creating a res.partner record, updating it, reading it, and deleting it. Uses Mocha and Should as dependencies.

If you are using default db name "odoo_db", username "admin", password "admin", and port 8069 on "http://localhost":

$ npm test 

If you aren't using the defaults, pass the variables in command line with environment variables:

$ ODOO_DB=mydatabase ODOO_USER=myusername ODOO_PW=mypassword ODOO_PORT=8080 > ODOO_BASE_URL=https://myodoo.com npm test 

I suspect there is a test oriented Odoo instance setup missing, but I can't say for sure. Updated steps here could also be useful for future setup of CI, via Github Workflow.

[vettloffah]

I removed some tests in version 3.1.0 that would only work on an empty odoo isntance. I believe it should work now with the instructions provided. Let me know if you try it out and still have issues.