Optimize dockerfile

Author: gdiggs

Dockerfile

@@ -3,8 +3,9 @@ FROM alpine:edge
 WORKDIR /usr/src/app
 
 RUN apk --update add nodejs git ruby ruby-dev build-base && \
-  apk del build-base && rm -fr /usr/share/ri && \
-  npm install -g mrb/ember-watson.git#95387b7
+  apk del build-base && rm -fr /usr/share/ri
+
+RUN npm install -g mrb/ember-watson.git#95387b7
 
 COPY . /usr/src/app