chore(gemspec): specify new Rails target, switch to new aws-sdk-s3 gem
chore(gemspec): specify new Rails target, switch to new aws-sdk-s3 gem

cortex-cms/cortex-plugins-core,cortex-cms/cortex-field_types-core,cortex-cms/cortex-field_types-core,cortex-cms/cortex-field_types-core,cortex-cms/cortex-plugins-core,cortex-cms/cortex-plugins-core