Add links to contribution guides

CODE_OF_CONDUCT.md

@@ -0,0 +1,5 @@
+# Code of Conduct
+
+Please refer to the [Nerves Project Code of Conduct], which applies to all `nerves-project` repositories.
+
+[Nerves Project Code of Conduct]: https://github.com/nerves-project/nerves/blob/master/CODE_OF_CONDUCT.md

CONTRIBUTING.md

@@ -0,0 +1,5 @@
+# Contributing
+
+Please refer to the [Nerves Project Contributing Guide], which applies to all `nerves-project` repositories.
+
+[Nerves Project Contributing Guide]: https://github.com/nerves-project/nerves/blob/master/CONTRIBUTING.md

ISSUE_TEMPLATE.md

@@ -0,0 +1,13 @@
+### Environment
+
+* Elixir version (`elixir -v`):
+* Nerves environment: (`mix nerves.env --info`)
+* Additional information about your host, target hardware or environment that
+  may help
+
+### Current behavior
+
+Include errors, stacktraces, screenshots or code that may help us reproduce the
+issue.
+
+### Expected behavior