readme update

version bump

mix.exs update

avoid compile time json dep

remove warning

updated travis

doc updates

implement exponential backoff with jitter according to the "full jitt…

…er" formula described at https://www.awsarchitectureblog.com/2015/03/backoff.html (ex-aws#185)

version bump

Merge branch 'master' of github.com:CargoSense/ex_aws