Add MOTD for Polly Vagrant

[davidvonthenen]

To help users figure out how to use rexray and polly...

[davidvonthenen]

Output of the MOTD when you log into either Vagrant instance:

----------------------------------------------
This host is running:
polly @ /usr/bin/polly
rexray @ /usr/bin/rexray

Sample commands for REX-Ray (can run on node0 or node1):
----------------------------------------------
Create a volume:
rexray volume create --volumename=node0vol --size=1

List volumes:
rexray volume


Sample commands for Polly (run on node0 only + must sudo su):
----------------------------------------------
Create a volume:
polly volume create --servicename=virtualbox --name=pollyvol --size=1

List volumes:
polly volume ls

Delete volume:
polly volume remove --volumeid=<Volume UUID>

----------------------------------------------

[davidvonthenen]

PR #115 has been merged and addresses this issue.