Simplify Dockerfile by using golang:onbuild image

Dockerfile

@@ -1,16 +1,6 @@
-FROM       ubuntu:13.10
+FROM       golang:onbuild
 MAINTAINER Prometheus Team <prometheus-developers@googlegroups.com>
 
-RUN        apt-get update && apt-get install -yq curl git mercurial gcc
-RUN        curl -s https://go.googlecode.com/files/go1.2.linux-amd64.tar.gz | tar -C /usr/local -xzf -
-ENV        PATH    /usr/local/go/bin:$PATH
-ENV        GOPATH  /go
-
-ADD        . /usr/src/node_exporter
-RUN        cd /usr/src/node_exporter && \
-           go get -d && go build && cp node_exporter /
-RUN        printf '{ "scrapeInterval": 10, "attributes": {} }' > \
-                  node_exporter.conf
-
-ENTRYPOINT [ "/node_exporter" ]
+ENTRYPOINT [ "go-wrapper", "run" ]
+CMD        [ "-logtostderr" ]
 EXPOSE     8080