Make Model Optimization Project Contributor Friendly

[alanchiao]

Master tracker issue for this.

At the minimum:

• we need to finish the first bullet point for infrastructure for open source.

Basic Doc for Contributors

• Pathway for recommending and contributing techniques (see this doc - initial version in PR - though RFC process needs to be finalized)
• Suggestions for other types of contributions (see this doc)

Basic Communication Channels

• Templates for technique requests / feature requests / bugs / etc.

Infrastructure for open source

• To accept pull requests (in the same veins as TensorFlow and other project) and accredit them to contributor. With the current infrastructure, any accepted pull requests would be overridden by the state of the code base within Google. (done: verified via Model clustering for Model Optimization Toolkit implementation #125, Test update CONTRIBUTED_TECHNIQUE.md #203, Only install enum34 for Python <= 3.4 #171 - still need to consider squashing commits).
• Open source continuous integration testing - started under https://github.com/tensorflow/model-optimization/tree/master/ci/kokoro.

Out-of-Scope

• Nightly builds

[813slim]

Thank you

[kfurkan08]

Thank you

[null9964]

Thx