[ZEPPELIN-1414] Remove CONTRIBUTING.md files

[corneadoug]

What is this PR for?

Following the PR #1356, we now have the contribution documentation to on Apache Zeppelin Website.

We can now remove the contributing files from the repository, and replace the links to that documentation.

What type of PR is it?

Documentation

What is the Jira issue?

https://issues.apache.org/jira/browse/ZEPPELIN-1414

How should this be tested?

Just check if there is other CONTRIBUTING.md files and if there is other links to replace

Questions:

• Does the licenses files need update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No

[AhyoungRyu]

@corneadoug There is one more "how to contribute" link - http://zeppelin.apache.org/docs/0.7.0-SNAPSHOT/#100-opensource :)

[corneadoug]

@AhyoungRyu Yes, this one could also be replaced.
There is actually a few pages of content inside the docs directory that we may want to move to the website later, so maybe we should create a JIRA issue for that migration too.

[jongyoul]

Good! I like it!

[felixcheung]

Not sure if it's important, having a file called Contributing.md, github actually automatically notifies the person creating a PR like this:

https://help.github.com/articles/setting-guidelines-for-repository-contributors/

[AhyoungRyu]

@felixcheung Yeah right. It makes sense. Then how about putting root CONTRIBUTING.md back and providing this link https://zeppelin.apache.org/contribution/contributions.html with proper message in that page? We can just let users know that our contribution guide is in Zeppelin website :)

[corneadoug]

@felixcheung Right, this message is showing if you have a CONTRIBUTING.md file in the root of the repository.
But we are also using the PR_TEMPLATE that github supports, and we have pretty much the same sentence inside of it: First time? Check out the contributing guide - https://zeppelin.apache.org/contribution/contributions.html

[felixcheung]

right, I'm not sure if that makes a difference to us

[corneadoug]

As long as it's still shown somewhere during the PR process, I think its fine?
Should we merge this then?

[AhyoungRyu]

LGTM 👍