Add CONTRIBUTING.md: Guidelines to contribute and submit code to CHaiDNN

CONTRIBUTING.md

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+## Contributor Guidelines
+
+Contributing code to this project is intended to be light weight and intuitive to users familiar with GitHub to actively encourage contributions, but a process is documented and should be followed to prevent chaos, confusion and despair.  
+
+## Mechanics of Contributing Code
+Firstly, in order to contribute code to this project, a contributor must have a valid and current [GitHub Account](https://help.github.com/articles/set-up-git) available to use.  Given an account,
+* The potential contributor forks this project into his/her account following the traditional [forking](https://help.github.com/articles/fork-a-repo) model native to GitHub
+* After forking, the contributor [clones their repository](https://help.github.com/articles/create-a-repo) locally on their machine
+* Code is developed and checked into the contributor's repository.  These commits are eventually pushed upstream to their GitHub repository
+* The contributor then issues a [pull-request](https://help.github.com/articles/using-pull-requests) against the **master** branch of this repository.
+
+At this point, the repository maintainers will be notified by GitHub that a 'pull request' exists pending against their repository.  A code review should be completed within a few days, depending on the scope of submitted code, and the code will either be accepted, rejected or commented on for extra feedback.
+
+## Code Submission Guidelines
+We want to ensure that the project code base maintains a level of quality over time, such that future contributors find it as easy to jump into the code as hopefully it is today.  As such, pull requests should
+* Remember that all of the code in this project is licensed under the [Apache License 2.0](http://www.apache.org/licenses/LICENSE-2.0). If you are not already familiar, please review the license before issuing a pull request.  We intend this project to be open to external contributors, and encourage developers to contribute code back that they believe will provide value to the overall community.  We will interpret an explicit 'pull request' back to this repository as an implicit acknowledgement from the contributor that they wish to share the code with the community under the terms of the Apche License 2.0.
+* Target the **master** branch in the repository
+
+Pull requests will be reviewed by the set of collaborators that are assigned for the repository. Pull requests may be accepted, declined or a conversation may start on the pull request thread with feedback. If the pull request is trivial and all the submission guidelines defined above are honored, the pull request may be accepted without delay. If the pull request is good, but the guidelines defined above are not followed, the collaborators may leave feedback on the pull request and engage in a conversation with the contributor with what they can do to improve the pull request.  At any time, collaborators may decline a pull request if they decide the contribution is not appropriate for the project, or the feedback from reviewers on a pull request is not being addressed in an appropriate amount of time.