rework layers

Dockerfile

@@ -1,9 +1,10 @@
 FROM node:8 as build
 WORKDIR /build
-COPY package.json package.json
+COPY .bowerrc bower.json ./
+RUN npm run bower install
+COPY package.json ./
 RUN npm install
 COPY . .
-RUN npm run bower install
 RUN npm run pub
 
 FROM nginx:mainline as runtime