Install npm 3 in docker (v3 warns on invalid peer dependencies instead of failing)

Dockerfile

@@ -4,6 +4,7 @@ ENV RAILS_ENV=production
 
 RUN echo 'deb http://httpredir.debian.org/debian jessie-backports main contrib non-free' >> /etc/apt/sources.list
 RUN apt-get update -qq && apt-get install -y build-essential libpq-dev libxml2-dev libxslt1-dev nodejs nodejs-legacy npm ffmpeg && rm -rf /var/lib/apt/lists/*
+RUN npm install -g npm@3
 RUN mkdir /mastodon
 
 WORKDIR /mastodon

package.json

@@ -10,9 +10,7 @@
     "browserify-incremental": "^3.1.1",
     "react": "^15.3.0",
     "react-dom": "^15.3.0",
-    "react-proxy": "^1.1.8"
-  },
-  "dependencies": {
+    "react-proxy": "^1.1.8",
     "axios": "^0.14.0",
     "es6-promise": "^3.2.1",
     "immutable": "^3.8.1",