Ignore build data with docker-compose

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

Dockerfile

@@ -21,6 +21,8 @@ ENV PATH="/root/.cargo/bin:$PATH"
 RUN mkdir /app
 WORKDIR /app
 
+
 RUN mix local.hex --force
+RUN mix local.rebar --force
 
 CMD mix run --no-halt