Add contributing.md

Author: timonv

CONTRIBUTING.md

@@ -0,0 +1,23 @@
+# The basics
+
+* Fork
+* Test
+* FMT
+* Pull Request
+
+# Using the Makefile
+
+```
+# Run all examples to see if they work.
+make examples
+```
+
+```
+# Format all go files, shortcut for go fmt ./...
+make fmt
+```
+
+```
+# Run all tests, shortcut for go test ./...
+make test
+```