Add contribution guidance

Add CONTRIBUTING.md that points to the same document in chef-cookbooks
Add mention of the contribution document in the top of the README.md
Merge pull request #119 from claco/contributing

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Offline compression enable by default on RHEL packages. Changing to be consistent with Ubuntu.
Merge pull request #120 from git-harry/master

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Use secure cookies when using https.
Merge pull request #121 from git-harry/master

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change default user role to _member_

fixes https://github.com/rcbops/chef-cookbooks/issues/558
Merge pull request #122 from willkelly/master

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Fixes https://github.com/rcbops/chef-cookbooks/issues/560. removing compress_offline setting for centos, using defaults now
Merge pull request #123 from jcannava/master

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added conditional for package name change
added required keys
changed reload to restart
add support for keystone multi SSL uri support
Merge pull request #124 from jrcloud/multi-keystone-ssl

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Making help_url an attribute and a variable passed to local_settings.py
Merge pull request #125 from jrcloud/de267-horizon-help-url

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added logic to change password_autocomplete attr in local_settings.py
fixing unnecessary string interpolation
Merge pull request #126 from jrcloud/horizon-auto-complete-passwd

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