fix tab in example

s3_url was incorrectly formatted in the example.
dynamically install rest-client
DRY RestClient
Merge pull request #36 from adamsb6/fix/34

dynamically install rest-client fix #34
s3_file version 2.5.1
(cherry picked from commit a2ec56e)
Use "path style" URL if bucket name contains a dot and URL is not specified manually