Got an unexpected keyword argument 'apikey' (out of date README?)

[c0bra]

Issue Summary

Following the docs in the README, if you specify the apikey as a keyword argument like so:

sendgrid.SendGridAPIClient(apikey=os.environ.get('SENDGRID_API_KEY'))

You will get the error:

Got an unexpected keyword argument 'apikey'

Other docs in this library show passing in api key as a regular argument, which works

sendgrid.SendGridAPIClient(os.environ.get('SENDGRID_API_KEY'))

Perhaps the docs need to be updated?

[childish-sambino]

Looks like both api_key and apikey used to be supported but now it's only api_key as of this #769

I've updated the README.