Create PULL_REQUEST_TEMPLATE.md

Author: Brad Micklea

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,17 @@
+### What does this PR do?
+
+### What issues does this PR fix or reference?
+
+### Previous behavior
+(Remove this section if not relevant)
+
+### New behavior
+(Explain the PR as it should appear in the release notes)
+
+Please review [Che's Contributing Guide](https://github.com/eclipse/che/blob/master/CONTRIBUTING.md) for best practices.
+
+### Tests written?
+Yes/No
+
+### Docs updated?
+Please add a matching PR to [the docs repo](http://github.com/eclipse/che-docs) and link that PR to this issue. Both will be merged at the same time.