lambda-cfn upload command

[alulsh]

We currently provide an upload.sh script to help people zip and upload code from their local machines to S3.

We could turn this into a more powerful lambda-cfn upload command to make this even easier for users. This command could also run automatically before running any lambda-cfn create or lambda-cfn update commands since it's common to forget to re-upload any changed code.

No urgency in working on this ticket - we can save this work for a later release. Leave any thoughts on this command and how it'd fit with other lambda-cfn commands in this ticket.

/cc @zmully @ianshward