Use make targets in the dockerfile

By dropping vendor & bindata.go from git unsee is no longer go installable, and realistically it won't be, because the build pipeline is big and involves multiple tools.
Let's just use make targets we use for development when building docker image.

.dockerignore

@@ -1,3 +0,0 @@
-Dockerfile
-Makefile
-unsee

.dockerignore

@@ -0,0 +1 @@
+.gitignore

Dockerfile

@@ -1,14 +1,10 @@
-FROM golang:1.8.3-alpine
-
+FROM golang:1.8.3-alpine as unsee-builder
 COPY . /go/src/github.com/cloudflare/unsee
-
 ARG VERSION
+RUN apk add --update make git nodejs
+RUN make -C /go/src/github.com/cloudflare/unsee VERSION="${VERSION:-dev}"
 
-RUN go install \
-    -ldflags "-X main.version=${VERSION:-dev}" \
-    github.com/cloudflare/unsee && \
-    rm -fr /go/src
-
+FROM golang:1.8.3-alpine
+COPY --from=unsee-builder /go/src/github.com/cloudflare/unsee/unsee /bin/unsee
 EXPOSE 8080
-
 CMD ["unsee"]