add users without sudo (gh_user_no_sudo)

It's handy to be able to create users that *don't* have sudo rights.
Here at Stanford we use this to add users to our VPC bastion box (ssh
proxy) so these users can use this machine for ssh tunneling, but I
don't want to give those users the keys to the kingdom.

This let's me configure a playbook like this.

   roles:
     - common
     - supervisor
     - role: gh_users
       gh_users:
         - su1
         - su2
         - su3
       gh_users_no_sudo:
         - normal1
         - normal2

The new gh_users_no_sudo list can be empty.
Update base AMIs.
Merge pull request #774 from edx/feanil/update-ansible-provision

Update base AMIs.
Merge pull request #742 from edx/sef/gh_users_no_sudo_master

add users without sudo (gh_user_no_sudo)
motd changes, add security banner

ssh login will look like this:

```
Welcome to Ubuntu 12.04.2 LTS (GNU/Linux 3.2.0-40-virtual x86_64)
*******************************************************************
*                                                                 *
*   _   _| |\ \/ /  This system is for the use of authorized      *
* / -_) _` | >  <   users only.  Usage of this system may be      *
* \___\__,_|/_/\_\  monitoried and recorded by system personnel.  *
*                                                                 *
* Anyone using this system expressly consents to such monitoring  *
* and is advised that if such monitoring reveals possible         *
* evidence of criminal activity, system personnel may provide the *
* evidence from such monitoring to law enforcement officials.     *
*                                                                 *
*******************************************************************

115 packages can be updated.
48 updates are security updates.

*** /dev/xvda1 will be checked for errors at next reboot ***

Last login: Tue Feb 11 18:58:37 2014 from terminus.mit.edu
```
using motd.tail

ssh login is now:

```
$ ssh jarv.m.sandbox.edx.org
Welcome to Ubuntu 12.04.2 LTS (GNU/Linux 3.2.0-40-virtual x86_64)

*** /dev/xvda1 will be checked for errors at next reboot ***

*** System restart required ***
*******************************************************************
*                                                                 *
*   _   _| |\ \/ /  This system is for the use of authorized      *
* / -_) _` | >  <   users only.  Usage of this system may be      *
* \___\__,_|/_/\_\  monitoried and recorded by system personnel.  *
*                                                                 *
* Anyone using this system expressly consents to such monitoring  *
* and is advised that if such monitoring reveals possible         *
* evidence of criminal activity, system personnel may provide the *
* evidence from such monitoring to law enforcement officials.     *
*                                                                 *
*******************************************************************
Last login: Tue Feb 11 19:12:12 2014 from terminus.mit.edu
````
sp
Merge pull request #776 from edx/jarv/ssh-motd

Jarv/ssh motd
optionally instruct logrotate to rotate logs to s3 buckets
adding task to create send-logs-to-s3 script
comment
adding custom rsyslog log rotate config
using includes for s3 sync
Added less-scary message for devstack
Merge pull request #784 from edx/will/devstack-motd

Added less-scary message of the day for devstack
switching to a single bash script instead of logrotate
remove logrotate script for rsyslog
fixing references to the bucket names
jinja fixes
jinja fix