added release information

RELEASE.md

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+# Java Wrapper Release Process
+
+ * code: https://github.com/watson-developer-cloud/java-wrapper
+ * maven: http://search.maven.org/#search%7Cga%7C1%7Ca%3A%22java-wrapper%22
+
+## Guide to uploading artifacts to the Central Repository
+
+We use sonatype as repository manager, it's used as the input channel for the Central Repository running the Sonatype Open Source Repository Hosting OSSRH service.
+
+### Prerequisites
+If you are not familiar with sonatype and/or the maven release process please read the following material:  
+ * Sonatype: http://central.sonatype.org/pages/apache-maven.html
+ * Releasing artifacts to Sonatype: http://kirang89.github.io/blog/2013/01/20/uploading-your-jar-to-maven-central/
+ * Install GPG and create a public key. More info: http://blog.sonatype.com/2010/01/how-to-generate-pgp-signatures-with-maven/#.VUL_DtNViko
+
+
+### Release steps
+
+  1. Make sure that `pom.xml` and `build.gradle` have the same version number. In the `pom.xml` file the version should ends with -SNAPSHOT
+
+  2. With the SCM connection configured correctly you can perform a release deployment to OSSRH (Staging) with:
+
+    `mvn release:clean release:prepare`
+
+    You will have to answer prompts for versions and tags. That will tag and commit a new version into your repository automatically.
+
+  3. Deploy to maven central:
+
+    `mvn release:perform`
+
+    This execution will deploy to OSSRH and release to the Central Repository in one go.