Added pull request template and modified README to include Jira link

patch by claudenw; reviewed by dritfx, dcapwell, josh-mckenzie, michaelsembwever for CASSANDRA-17837

.github/pull_request_template.md

@@ -0,0 +1,25 @@
+Thanks for sending a pull request! Here are some tips if you're new here:
+
+ * Ensure you have added or run the [appropriate tests](https://cassandra.apache.org/_/development/testing.html) for your PR
+ * Be sure to keep the PR description updated to reflect all changes.
+ * Write your PR title to summarize what this PR proposes.
+ * If possible, provide a concise example to reproduce the issue for a faster review.
+ * Read our [contributor guidelines](https://cassandra.apache.org/_/development/index.html)
+ * If you're making a documentation change, see our [guide to documentation contribution](https://cassandra.apache.org/_/development/documentation.html)
+
+Commit messages should follow the following format:
+
+```
+<One sentence description, usually Jira title or CHANGES.txt summary>
+
+<Optional lengthier description (context on patch)>
+
+patch by <Authors>; reviewed by <Reviewers> for CASSANDRA-#####
+
+Co-authored-by: Name1 <email1>
+Co-authored-by: Name2 <email2>
+
+```
+
+The [Cassandra Jira](https://issues.apache.org/jira/projects/CASSANDRA/issues/)
+

README.asc

@@ -9,6 +9,8 @@ https://cwiki.apache.org/confluence/display/CASSANDRA2/DataModel[Row store] mean
 
 For more information, see http://cassandra.apache.org/[the Apache Cassandra web site].
 
+Issues should be reported on The https://issues.apache.org/jira/projects/CASSANDRA/issues/[The Cassandra Jira].
+
 Requirements
 ------------
 . Java >= 1.8 (OpenJDK and Oracle JVMS have been tested)