Issue template for retrofit.

.github/ISSUE_TEMPLATE.md

+What kind of issue is this?
+
+ - [ ] Question. This issue tracker is not the place for questions. If you want to ask how to do
+       something, or to understand why something isn't working the way you expect it to, use Stack
+       Overflow. https://stackoverflow.com/questions/tagged/retrofit
+
+ - [ ] Bug report. If you’ve found a bug, spend the time to write a failing test. Bugs with tests
+       get fixed. Here’s an example: https://gist.github.com/swankjesse/6608b4713ad80988cdc9
+
+ - [ ] Feature Request. Start by telling us what problem you’re trying to solve. Often a solution
+       already exists! Don’t send pull requests to implement new features without first getting our
+       support. Sometimes we leave features out on purpose to keep the project small.