Add contribution guide (#299)

Author: vancexu

CONTRIBUTING.md

@@ -0,0 +1,55 @@
+# Developing cadence-java-client
+
+This doc is intended for contributors to `cadence-java-client` (hopefully that's you!)
+
+**Note:** All contributors also need to fill out the [Uber Contributor License Agreement](http://t.uber.com/cla) before we can merge in any of your changes
+
+## Development Environment
+
+* Java 8.
+* Gradle build tool
+* Docker
+
+## Licence headers
+
+This project is Open Source Software, and requires a header at the beginning of
+all source files. To verify that all files contain the header execute:
+
+```lang=bash
+./gradlew licenseCheck
+```
+
+To generate licence headers execute
+
+```lang=bash
+./gradlew licenseFormat
+```
+
+## Commit Messages
+
+Overcommit adds some requirements to your commit messages. At Uber, we follow the
+[Chris Beams](http://chris.beams.io/posts/git-commit/) guide to writing git
+commit messages. Read it, follow it, learn it, love it.
+
+## Test and Build
+
+Testing and building cadence-java-client requires running cadence docker locally, execute:
+
+```bash
+curl -O https://raw.githubusercontent.com/uber/cadence/master/docker/docker-compose.yml
+docker-compose up
+```
+
+(If this does not work, see instructions for running the Cadence Server at https://github.com/uber/cadence/blob/master/README.md.)
+
+Then run all the tests with:
+
+```bash
+./gradlew test
+```
+
+Build with:
+
+```bash
+./gradlew build
+```

README.md

@@ -24,7 +24,7 @@ If this does not work, see instructions for running the Cadence Server at https:
 
 [CLI is avaialable as an executable or as a docker image](https://github.com/uber/cadence/blob/master/tools/cli/README.md)
 
-# Build a configuration
+## Build a configuration
 
 Add *cadence-client* as a dependency to your *pom.xml*:
 
@@ -38,9 +38,14 @@ or to *build.gradle*:
 
     compile group: 'com.uber.cadence', name: 'cadence-client', version: '2.4.1'
 
-# Documentation
+## Documentation
 
-The documentation on how to use the Cadence Java client is [here](https://cadenceworkflow.io/docs/javaclient/).
+The documentation on how to use the Cadence Java client is [here](https://cadenceworkflow.io/docs/04_javaclient/).
 
 Javadocs for the client API are located [here](https://www.javadoc.io/doc/com.uber.cadence/cadence-client).
 
+## Contributing
+We'd love your help in making the Cadence Java client great. Please review our [contribution guidelines](CONTRIBUTING.md).
+
+## License
+Apache License, please see [LICENSE](LICENSE) for details.