Ask for password input if password is not specified in the command or in...

... the .pypirc config file

I added added the getpass module to ask for password input if the -p flag contains no password or if the password is not specified in the config. I'd rather not store my password on disk or in a config file if possible. This allows me to specify my password at runtime. I believe this is the same behavior as the setup.py upload command.

I moved the username and password outside of the request function so getpass does not ask you for your password for each file to be uploaded.