removing symlink. Adding contributing guidelines back (apache#3450)

* removing symlink.  Adding contributing guidelines back

* clean up

CONTRIBUTING.md

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+<!--
+    Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements.  See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.  The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing,
+    software distributed under the License is distributed on an
+    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+    KIND, either express or implied.  See the License for the
+    specific language governing permissions and limitations
+    under the License.
+-->
+
+## Contributing to Heron
+
+Discussion about Heron happens on GitHub and over the mailing list.
+
+* GitHub: [apache/incubator-heron](https://github.com/apache/incubator-heron)
+* Heron User Group: [[email protected]](https://mail-archives.apache.org/mod_mbox/heron-user/)
+
+Community is critical to Heron. Contributions are welcomed!
+
+
+## How Can I Contribute to Heron?
+
+You can first read the following pages to have a basic understanding
+of Heron:
+
+* [Heron Architecture](https://heron.incubator.apache.org/docs/heron-architecture/)
+* [Compiling Heron](https://heron.incubator.apache.org/docs/compiling-overview/)
+* [Heron Codebase](https://heron.incubator.apache.org/docs/compiling-code-organization/)
+
+Heron includes a script to bootstrap an IntelliJ IDEA project. The project includes support for Heron
+code styles and copyright headers. 
+
+To bootstrap an IDEA project run the following from the root folder of the repo::
+
+```bash
+$ ./scripts/setup-intellij.sh
+```
+To bootstrap an Eclipse project fun the following from the root folder of the repo:
+
+```bash
+$ ./scripts/setup-eclipse.sh
+```
+
+In general, contributions that fix bugs or add features (as opposed to stylistic, refactoring, or
+"cleanup" changes) are preferred. If you're looking for places to contribute, issues with label
+[help-wanted](https://github.com/apache/incubator-heron/issues?q=is%3Aopen+is%3Aissue+label%3Ahelp-wanted)
+are good candidates. Please check with the [mailing list](https://mail-archives.apache.org/mod_mbox/heron-dev/)
+if your patch involves lots of changes.
+
+**If you have any question or issues about troubleshooting**,
+you should post on [mailing list](https://mail-archives.apache.org/mod_mbox/heron-user/) instead
+of opening GitHub issues.
+
+### Submitting a Patch
+1. Discuss your plan and design, and get agreement on
+[mailing list](https://mail-archives.apache.org/mod_mbox/heron-dev/).
+
+2. Implement proper unit tests along with your change. Verify that all tests can pass.
+
+3. Submit a GitHub pull request that includes your change and test cases.
+Describe clearly in your pull request the changes made. Verify that Travis CI passes.
+
+4. Complete a code review by addressing the reviewer's comments.
+
+5. A project committer will merge the patch to the master branch.