Made the repository configurable

Dockerfile

@@ -2,6 +2,8 @@ FROM alpine:edge
 MAINTAINER Jan Christian Grünhage <mail@janchristiangruenhage.de>
 
 ENV GOPATH /gopath
+ENV CADDY_REPO_OWNER mholt
+ENV CADDY_REPO_NAME caddy
 ENV CADDY_BRANCH unbuffered_proxy
 ENV CADDYPATH /caddy
 ENV UID 192
@@ -12,12 +14,12 @@ RUN addgroup -g $GID -S caddy \
 
 RUN apk add --update musl \
 	&& apk add --no-cache build-base libcap tini go git \
-	&& mkdir -p $GOPATH/src/github.com/mholt \
-	&& cd $GOPATH/src/github.com/mholt \
-	&& git clone https://github.com/mholt/caddy \
-	&& cd caddy \
+	&& mkdir -p $GOPATH/src/github.com/$CADDY_REPO_OWNER \
+	&& cd $GOPATH/src/github.com/$CADDY_REPO_OWNER \
+	&& git clone https://github.com/$CADDY_REPO_OWNER/$CADDY_REPO_NAME \
+	&& cd $CADDY_REPO_NAME \
 	&& git checkout $CADDY_BRANCH \
-	&& go get github.com/mholt/caddy/... \
+	&& go get github.com/$CADDY_REPO_OWNER/$CADDY_REPO_NAME/... \
 	&& mv $GOPATH/bin/caddy /usr/bin \
 	&& setcap cap_net_bind_service=+ep /usr/bin/caddy \
 	&& apk del --purge build-base go \