Introduce a switch for sandbox and dev enviroments

[clemens7haar]

Hello,

To make this script work with sandboxes and developer enviroments I added some small changes.

A "production_instance" parameter was added to the PardotAPI class. By default it's set to True, but if you define it as False it changes the necessary servernames.

if production_instance == True:
  self.domain` = 'https://pi.pardot.com'
  self.oauth_domain = 'https://login.salesforce.com/'
else:
  """Sandbox or developer environment"""
 self.domain = 'https://pi.demo.pardot.com'
 self.oauth_domain = 'https://test.salesforce.com/'

You can use it like this:

from pypardot.client import PardotAPI
p = PardotAPI(version=4, production_instance=False)
p.setup_salesforce_auth_keys()

Maybe this option is useful for other people too.