Redirect new docker port 2375

[jonnyzzz]

Docker 1.0.0 appears to use 2375 port instead of older 4243

[robparrott]

As noted elsewhere, the current setup makes vagrant+docker unusable for anyone who uses CrashPlan for backup, since Docker was using an unregistered port. Hope you'll update this soon.

[mitchellh]

This looks liek its already happening!