Added make target to update Docker images

Added Support for Docker Sync

Docker Sync will alleviate some of the filesystem issues on OS X.

Upgraded to Mongo 3.0

Fixes openedx-unsupported#52

Added info on restarting services to README

Fixes openedx-unsupported#36

Disabled host volume for edxapp

The settings have not yet been merged. The host volume should only be used if the local repository has been rebased on the branch in https://github.com/edx/edx-platform/pull/14376.

ECOM-6634