Make CoreDNS a server type plugin for Caddy (#220)

* Make CoreDNS a server type plugin for Caddy

Remove code we don't need and port all middleware over. Fix all tests
and rework the documentation.

Also make `go generate` build a caddy binary which we then copy into
our directory. This means `go build`-builds remain working as-is.

And new etc instances in each etcd test for better isolation.
Fix more tests and rework test.Server with the newer support Caddy offers.

Fix Makefile to support new mode of operation.

.travis.yml

@@ -12,7 +12,7 @@ go:
 # In the Travis VM-based build environment, IPv6 networking is not
 # enabled by default. The sysctl operations below enable IPv6.
 # IPv6 is needed by some of the CoreDNS test cases. The VM environment
-# is needed to have access to sudo in the test environment. Sudo is 
+# is needed to have access to sudo in the test environment. Sudo is
 # needed to have docker in the test environment. Docker is needed to
 # launch a kubernetes instance in the test environment.
 # (Dependencies are fun! :) )
@@ -38,9 +38,9 @@ before_script:
   - if which docker &>/dev/null ; then docker pull gcr.io/google_containers/hyperkube-amd64:v1.2.4 ; docker ps -a ; fi
   - if which docker &>/dev/null ; then ./contrib/kubernetes/testscripts/start_k8s_with_services.sh ; docker ps -a ; fi
   # Get golang dependencies, and build coredns binary
-  - go get -v -d
+  - go get -v -d ./...
   - go get github.com/coreos/go-etcd/etcd
-  - go build -v -ldflags="-s -w"
+    #- go build -v -ldflags="-s -w"
 
 script:
   - go test -tags etcd -race -bench=. ./...