Add support for S3 through the REST API

This is currently using the old S3 authentication
(https://s3.amazonaws.com/doc/s3-developer-guide/RESTAuthentication.html),
in order to support Exoscale Storage

Refs #112

.travis.yml

@@ -4,12 +4,10 @@ rvm:
   - 2.4.1
 services:
   - redis-server
-before_install:
-  - gem install bundler
 before_script:
-  - cp config.yml.example config.yml
+  - cp config.yml.example.$BACKEND config.yml
   - mkdir -p tmp && echo "swifttoken" > tmp/swift_token.txt
-script: ruby spec/swift/*
+script: ruby spec/$BACKEND/*
 branches:
   only:
     - master
@@ -21,3 +19,6 @@ notifications:
       - http://hook-juggler.herokuapp.com/hooks/travis
     on_success: always
     on_failure: always
+env:
+  - BACKEND=s3
+  - BACKEND=swift