Add a configure subcommand to bootstrap creation of config file

[garnaat]

It would be helpful to add a subcommand aws configure that would create an initial configuration file for the user in the default location ~/.aws/config. This subcommand could look for existing credentials from boto or from legacy AWS CLI tools and include those credentials.

[sopel]

This has been addressed by #455 (and subsequent improvements to this feature) - it seems to be available as of version 1.2.3.