Add issue and PR template

To reduce issue volume on GitHub all support question should be redirected
to StackOverflow or Gitter.

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,29 @@
+This is:
+
+- [ ] a bug report
+- [ ] a feature request
+- [ ] **not** a usage question (ask them on https://stackoverflow.com/questions/tagged/phpspreadsheet or https://gitter.im/PHPOffice/PhpSpreadsheet)
+
+### What is the expected behavior?
+
+
+### What is the current behavior?
+
+
+### What are the steps to reproduce?
+
+Please provide a [Minimal, Complete, and Verifiable example](http://stackoverflow.com/help/mcve) of code that exhibits the issue without relying on an external Excel file or a web server:
+
+```php
+<?php
+
+require __DIR__ . '/vendor/autoload.php';
+
+// Create new Spreadsheet object
+$spreadsheet = new \PhpOffice\PhpSpreadsheet\Spreadsheet();
+
+// add code that show the issue here...
+```
+
+
+### Which versions of PhpSpreadsheet and PHP are affected?

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,14 @@
+This is:
+
+- [ ] a bugfix
+- [ ] a new feature
+
+Checklist:
+
+- [ ] Changes are covered by unit tests
+- [ ] Code style is respected
+- [ ] Commit message explains **why** the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
+- [ ] CHANGELOG.md contains a short summary of the change
+- [ ] Documentation is updated as necessary
+
+What does it change?