shorten IAM role names to allow for longer stack names (max size is 6…

…4 chars)

- Allow specification of maximum image size; will return a HTTP 400 w…

…hen exceeded

- Allow whitelisting of target dimensions; will return HTTP 400 when other sizes are requested
- sharp to 0.25.3 (from 0.23.4)
- Error in explicit size parsing for sizes < 100px

Allow width & height in URLs (overrides the base64 values)

integrate changes from upstream v4.2

initial release