Add TestServer (#102)

Add a fullblown testing server. This allows us to do integration tests.

Also add a basic proxy test. Further tests will test etcd proxy
and stub zone communication and other "wildish" configurations.
Redo the server startup, so we can access the ports it listens on when
it has started up (with dns.ActivateAndServer).

Extend the .travis file to download etcd and test for that as well.

Put integration tests in test dir

.travis.yml

@@ -1,7 +1,12 @@
 language: go
-sudo: false
 go:
   - 1.5
   - 1.6
+before_script:
+  - go get github.com/coreos/etcd
+  - go get github.com/coreos/go-etcd/etcd
+  - go build -o $HOME/gopath/src/github.com/coreos/etcd/etcd.run github.com/coreos/etcd
+  - $HOME/gopath/src/github.com/coreos/etcd/etcd.run &
+  - sleep 2
 script:
-  - go test -race -bench=. ./...
+  - go test -tags etcd -race -bench=. ./...