switch base to alpine edge

isso/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.3
+FROM alpine:edge
 MAINTAINER Wonderfall <wonderfall@mondedie.fr>
 
 ARG ISSO_VER=0.10.4
@@ -6,26 +6,24 @@ ARG ISSO_VER=0.10.4
 ENV GID=1000 UID=1000
 
 RUN echo "@commuedge http://nl.alpinelinux.org/alpine/edge/community" >> /etc/apk/repositories \
- && apk -U add \
-    python \
+ && BUILD_DEPS=" \
     python-dev \
     libffi-dev \
-    py-setuptools \
     py-pip \
+    build-base" \
+ && apk -U add \
+    ${BUILD_DEPS} \
+    python \
+    py-setuptools \
     sqlite \
     ca-certificates \
-    build-base \
     su-exec \
     tini@commuedge \
  && pip install --no-cache cffi \
  && pip install --no-cache misaka==1.0.2 \
  && wget https://github.com/posativ/isso/releases/download/$ISSO_VER/isso-$ISSO_VER.tar.gz -P /tmp \
  && pip install /tmp/isso-$ISSO_VER.tar.gz \
- && apk del \
-    python-dev \
-    libffi-dev \
-    py-pip \
-    build-base \
+ && apk del ${BUILD_DEPS} \
  && rm -rf /var/cache/apk/* /tmp/*
 
 COPY run.sh /usr/local/bin/run.sh