Update nodebb to 1.5.3

Dockerfile

@@ -6,7 +6,7 @@ WORKDIR /app/code
 
 ENV PATH /usr/local/node-6.9.5/bin:$PATH
 
-RUN curl -L https://github.com/NodeBB/NodeBB/archive/v1.5.1.tar.gz | tar -xz --strip-components 1 -f -
+RUN curl -L https://github.com/NodeBB/NodeBB/archive/v1.5.3.tar.gz | tar -xz --strip-components 1 -f -
 ADD config.json.template /app/code
 RUN npm install --production
 RUN npm install nodebb-plugin-emailer-local