[x] Add a command evalai login <username> which will prompt for the password.
[x] Once the password is entered, then the command will create a auth_token for the user by using the EvalAI login API, & saves it in the token.json file at ~/.evalai/token.json in the user's system.
Fixes #137
Deliverables
evalai login <username>
which will prompt for thepassword
.token.json
file at~/.evalai/token.json
in the user's system.