Scope aws-skd to version 2 (#34)

Since we use new aws-sdk API, I've scoped aws-sdk version
so someone doesn't accidentaly installs wrong version during the
development.

Author: dixpac

Gemfile

@@ -8,5 +8,5 @@ gem 'byebug'
 gem 'sqlite3'
 gem 'httparty'
 
-gem 'aws-sdk', require: false
+gem 'aws-sdk', '~> 2', require: false
 gem 'google-cloud-storage', require: false

Gemfile.lock

@@ -138,7 +138,7 @@ PLATFORMS
 
 DEPENDENCIES
   activestorage!
-  aws-sdk
+  aws-sdk (~> 2)
   bundler (~> 1.15)
   byebug
   google-cloud-storage