Freebird: go-subscriptions

This is the old `go-subscriptions` plugin minus recurly-specific stuff.

see https://github.com/GigaOM/legacy-pro/issues/4125
weird spacing, perhaps my browser?

![screen shot 2014-09-23 at 6 54 54 am](https://cloud.githubusercontent.com/assets/1709697/4373033/5fc4d842-4329-11e4-8185-740f35337b2d.png)