Explicit Login

[timdorr]

Switches the API for the client from:

TeslaApi::Client.new(email, password, client_id, client_secret)

to:

client = TeslaApi::Client.new(email, client_id, client_secret)
client.login!(password)

This is necessary for re-use of tokens across instances of the client. Right now, I've got a process checking the API once a minute and I know that's creating spurious access tokens in their system.