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 #50 from claco/contributing

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Check for missing server_id node attribute.
Merge pull request #51 from git-harry/master

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Fix replication issues

* Fixes Issue #527 more correctly
* Fixes replication password
* Removes unused variables
* Removes developer mode since generated passwords are easily accessible
Merge pull request #52 from Apsu/issue527

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Merge pull request #53 from rackerjoe/grizzly

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Updating version # to 4.1.2