make log level configurable

fixes #22
bump version
adding responds_to to allow usage with thin

There's strange behavior where server.config would equal 1024 when running
fake_dynamo under thin, a superior web server, instead of the, frankly
terrible, WEBrick. This is a stop-gap fix that allows thin to run unhinged.
check if server responds to config

puma doesn't responds to config
bump version
put item only supports NONE and ALL_OLD
use strict versions of base64

fixes #24
readme update
update readme
remove sets if they empty out
add test for empty sets
add changelog
bump version
show date in changelog