Fixed memcached to be compatible with cf 138

Applied the following fixes:
1. Updated vcap-services-base and vcap-common to version used by [mysql-services](https://github.com/cloudfoundry/cf-services-release/blob/master/src/mysql_service/Gemfile.lock#L2-L31)
2. [Downgraded activesupport](https://github.com/cloudfoundry/cf-services-release/commit/51d40ec8e700b1178b0a44ec474d16d9a4b1d2a4)
3. Added `provider_name` [because](https://github.com/cloudfoundry/vcap-services-base/blob/master/lib/base/gateway_service_catalog.rb#L51-L66) of [extra field requirement](https://github.com/cloudfoundry/vcap-services-base/blob/master/lib/base/service.rb#L24)
4. Also added `extra` to plans to be [in line with mysql](https://github.com/cloudfoundry/cf-services-release/blob/master/jobs/mysql_gateway/templates/mysql_gateway.yml.erb#L38).