use node base image instead of ubuntu

tests/apps/dockerfile-procfile/Dockerfile

@@ -1,14 +1,9 @@
-FROM ubuntu:trusty
-ENV LC_ALL C
-ENV DEBIAN_FRONTEND noninteractive
-ENV DEBCONF_NONINTERACTIVE_SEEN true
+FROM node:4
+
 EXPOSE 3001/udp
 EXPOSE  3000/tcp
 EXPOSE 3003
 
-RUN apt-get install -y software-properties-common && add-apt-repository ppa:chris-lea/node.js && apt-get update
-RUN apt-get install -y build-essential curl postgresql-client-9.3 nodejs git
-
 COPY . /app
 WORKDIR /app
 RUN npm install