Removed hard sync lib dependency, moved to suggest to reduce install footprint

Author: sebastianfeldmann

composer.json

@@ -26,18 +26,18 @@
         "ext-dom": "*",
         "ext-json": "*",
         "ext-spl": "*",
-        "barracuda/copy": "1.1.*",
-        "dropbox/dropbox-sdk": "1.1.*",
         "phpunit/php-timer": "~1.0.2",
         "sebastian/environment": "~1.1",
         "sebastian/version": "~1.0",
         "swiftmailer/swiftmailer": "5.3.*",
-        "aws/aws-sdk-php": "2.7.*",
         "symfony/event-dispatcher": "2.6.*"
     },
     "suggest": {
+        "barracuda/copy": "Require '1.1.*' to sync to copy.com",
+        "dropbox/dropbox-sdk": "Require '1.1.*' to sync to Dropbox",
+        "aws/aws-sdk-php": "Require '2.7.*' to sync to Amazon S3",
         "phpseclib/phpseclib": "Require '2.0.*@dev' to use SFTP sync",
-        "softlayer/objectstorage": "Require 'dev-master' to use softlayer sync"
+        "softlayer/objectstorage": "Require 'dev-master' to sync to Softlayer"
     },
     "bin": [
         "phpbu"