check to verify keys

ability to download files

download and concat files

error message for no urls

moved download command to s3.rb

added aws-sdk into dependencies

added stubs for aws s3

finish testing and functionality of s3::download

modifications to match bucket and key behaviour

clean up code for tests

changed s3:download to s3:getmerge

added get and getmerge

updated to address bug in buckets.exist on aws sdk, unit test support for changes to s3:get/getmerge

moved get and get merge logic to seperate function

moved controller logic to a s3 module

moved s3_object decleration to be done once

moved attempt for getting s3 objects to new function

changes to match comments

moved s3_faker to only files used by it

changed s3 host to use URI

changes to match comments from @dd

removed unused functions

revert controller, changed get_file to is_file

file comments

pulled path_is_root_file_of_key into new function
reverted files back to master
Merge branch 'cngan_local_download' of https://github.com/mortardata/mortar into cngan_local_download