first docker-driven integration test

adds a docker-driven integration test

**scenario**
* three nodes: `bootstrap`, `server`, `client`

1. boostrap enters network
1. server and client connect
1. server adds randomly generated file (client waits for signal to add file)
1. server sends signal then client adds the file
1. client verifies file
1. all nodes exit

it would be cool if `ipfs daemon` could fork on its own after its finished the setup, eliminating the need to wait for it to boot up.