Provide environment variables for config options (closes #161)

Change-Id: Iacb5902f4206fbf0a7a5bd6979aae4fe7a3be914
diff --git a/Dockerfile b/Dockerfile
index 5da636d..7b41b18 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -23,7 +23,7 @@
 RUN addgroup -S korap && \
     adduser -S export -G korap && \
     mkdir export && \
-    chown -R export.korap /export
+    chown -R export:korap /export
 
 WORKDIR /export