Make iso scripts require ruby 1.9.3 or higher

[Vladimir Sharshov]

A few days ago (i think yesterday ) make iso do not build iso if we system use Ruby 1.8.7 (default for Ubuntu 12.04). This is not bad, but we should add information about this obviously.
Doc in http://docs.mirantis.com/fuel-dev/develop/env.html#building-the-fuel-iso only talk about Ruby in context of Ubuntu 12.10 (which use Ruby 1.9.3, but it is necessary to know)

   Installing rake (10.2.0)
   Gem::InstallError: rake requires Ruby version >= 1.9.
   An error occurred while installing rake (10.2.0), and Bundler cannot continue.
   Make sure that `gem install rake -v '10.2.0'` succeeds before bundling.

[Mike Scherbakov (mihgen)]

It is critical to keep this piece of documentation always up to date.

[Vladimir Sharshov (vsharshov)]

Workaround of Ubuntu 12.04:

   sudo apt-get --purge remove ruby-rvm
   sudo rm -rf /usr/share/ruby-rvm /etc/rvmrc /etc/profile.d/rvm.sh
   \curl -sSL https://get.rvm.io | bash -s stable
   source ~/.bash_profile # Or just open new session
   rvm install 1.9.3
   rvm use 1.9.3

And now before start building iso just use `rvm use 1.9.3` or set this Ruby as default:
  rvm --default use 1.9.3

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/83095

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/83095
Committed: https://git.openstack.org/cgit/stackforge/fuel-main/commit/?id=5505a5495402b9e43dbd4dd7a816530fe396872e
Submitter: Jenkins
Branch: master

commit 5505a5495402b9e43dbd4dd7a816530fe396872e
Author: Roman Vyalov <email address hidden>
Date: Wed Mar 26 19:13:46 2014 +0400

    Freeze version of rake gems

    Change-Id: Ib5af3efde0b2edd2401e85a143119bc13d21d9b2
    Closes-Bug: #1297664

[Andrew Woodward (xarses)]

Please backport

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/4.1
Review: https://review.openstack.org/93573

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/93573
Committed: https://git.openstack.org/cgit/stackforge/fuel-main/commit/?id=9e12dcce4ebfbd608910481570c721720fbf1edc
Submitter: Jenkins
Branch: stable/4.1

commit 9e12dcce4ebfbd608910481570c721720fbf1edc
Author: Roman Vyalov <email address hidden>
Date: Wed Mar 26 19:13:46 2014 +0400

    Freeze version of rake gems

    Change-Id: Ib5af3efde0b2edd2401e85a143119bc13d21d9b2
    Closes-Bug: #1297664
    (cherry picked from commit 5505a5495402b9e43dbd4dd7a816530fe396872e)