Upgrade docker to 1.6.3

Also update the acceptance test suite to compose 1.8.0-rc2.

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

Author: vdemeester

Dockerfile

@@ -1,5 +1,5 @@
 # This file describes the standard way to build libcompose, using docker
-FROM golang:1.6.2
+FROM golang:1.6.3
 
 
 # virtualenv is necessary to run acceptance tests
@@ -39,7 +39,7 @@ WORKDIR /go/src/github.com/docker/libcompose
 
 # Compose COMMIT for acceptance test version, update that commit when
 # you want to update the acceptance test version to support.
-ENV COMPOSE_COMMIT 1.8.0-rc1
+ENV COMPOSE_COMMIT 1.8.0-rc2
 RUN virtualenv venv && \
     git clone https://github.com/docker/compose.git venv/compose && \
     cd venv/compose && \