Fix Dockerfile

* Change build artifact directory from build/maven to target/
  `docker builds` fail at 'mv
build/maven/aws-apigateway-*-jar-with-dependencies.jar
/aws-apigateway-importer.jar' because maven is
building into target/ instead.

* Do not attempt to remove /root/.m2
  The Maven Docker image exports /root/.m2 so `rm -rf ~/.m2` fails. See
https://github.com/carlossg/docker-maven/blob/8ab542b907e69c5269942bcc0915d8dffcc7e9fa/jdk-8/Dockerfile#L11
for reference.

Author: Ryan Walker

Dockerfile

@@ -10,9 +10,8 @@ COPY tst /app/tst/
 WORKDIR /app
 
 RUN mvn assembly:assembly \
-    && mv build/maven/aws-apigateway-*-jar-with-dependencies.jar /aws-apigateway-importer.jar \
-    && mvn clean \
-    && rm -rf /app ~/.m2
+    && mv target/aws-apigateway-*-jar-with-dependencies.jar /aws-apigateway-importer.jar \
+    && mvn clean
 
 VOLUME ["/root/.aws"]
 VOLUME ["/data"]