botocore: 1.12.48 -> 1.12.62

boto3: 1.9.36 -> 1.9.62
awscli: 1.16.72

I update all three of these at a time because they rely on each other
and get annoyed when such changes are non-atomic. Also added a note to
the packages telling people that this is needed. I tested awscli and the
libraries against a real account.