Update README.md to include ansible version

[adammeghji]

Ansible version needs to be >= 1.7, otherwise mesos_install_mode="slave" does not get set correctly, and slaves get set up as master nodes.

👎 ANSIBLE 1.6:

TASK: [ansible-mesos | debug msg="Install Mode is slave"] *********************
ok: [ec2-54-87-91-235.compute-1.amazonaws.com] => {
    "item": "",
    "msg": "Install Mode is master"
}
ok: [ec2-54-235-237-69.compute-1.amazonaws.com] => {
    "item": "",
    "msg": "Install Mode is master"
}
ok: [ec2-54-234-24-109.compute-1.amazonaws.com] => {
    "item": "",
    "msg": "Install Mode is master"
}

👍 ANSIBLE 1.7:

TASK: [ansible-mesos | debug msg="Install Mode is slave"] *********************
ok: [ec2-54-87-91-235.compute-1.amazonaws.com] => {
    "msg": "Install Mode is slave"
}
ok: [ec2-54-235-237-69.compute-1.amazonaws.com] => {
    "msg": "Install Mode is slave"
}
ok: [ec2-54-234-24-109.compute-1.amazonaws.com] => {
    "msg": "Install Mode is slave"
}

[mhamrah]

Thanks for the FYI!

[adammeghji]

No problem! I really really appreciate the work you've put into this -- it's been very inspiring and helpful. 🙇

I've actually got a number of other supplementary scripts / Makefiles / etc. which I'm using to implement a complete solution on EC2, hopefully I'll have some more contributions to share back with you. 👍

Cheers!