(QENG-758) add ability to select a group a beaker hosts based upon...

...a set of properties

- a shortcut means of selecting a sub group of hosts to run commands on
(gh-333) Typo in method name ('has' instead of 'hash') in ...

... options_hash.rb (line 101)

- yup, fix the typo
Merge pull request #296 from anodelman/confine-agents

(QENG-758) add ability to select a group a beaker hosts based upon...
Merge pull request #369 from anodelman/options-hash

(gh-333) Typo in method name ('has' instead of 'hash') in ...
(QENG-941) create contributor documentation for beaker

- create CONTRIBUTING.md
- covers steps necessary before PRs will be merged into Beaker
Merge pull request #365 from anodelman/maint

(QENG-941) create contributor documentation for beaker
(QENG-967) Disable iptables on el hosts bringup.

Also fixes bug in `disable_iptables` where per-array-element was invoking wrong
method. Looks like `disable_iptables` was originally copied from
`copy_ssh_to_root`

Also adds rspec for Beaker::Hypervisor.configure

Signed-off-by: Wayne <wayne@puppetlabs.com>