Add support for shm_size. Fixes #2823.

shm_size controls the size of /dev/shm in the container and requires
Docker 1.10 or newer (API version 1.22).  This requires docker-py 1.8.0
(docker/docker-py#923).

Similar to fields like `mem_limit`, `shm_size` may be specified as
either an integer or a string (e.g., `64M`).

Updating docker-py to the master branch in order to get the unreleased
dependency on `shm_size` there in place.

Signed-off-by: Spencer Rinehart <anubis@overthemonkey.com>

compose/service.py

@@ -57,6 +57,7 @@ DOCKER_START_KEYS = [
     'volumes_from',
     'security_opt',
     'cpu_quota',
+    'shm_size',
 ]
 
 
@@ -654,6 +655,7 @@ class Service(object):
             ipc_mode=options.get('ipc'),
             cgroup_parent=options.get('cgroup_parent'),
             cpu_quota=options.get('cpu_quota'),
+            shm_size=options.get('shm_size'),
         )
 
     def build(self, no_cache=False, pull=False, force_rm=False):