Add getting setup to contributing.

CONTRIBUTING.md

@@ -2,6 +2,10 @@
 
 Moto has a [Code of Conduct](https://github.com/spulec/moto/blob/master/CODE_OF_CONDUCT.md), you can expect to be treated with respect at all times when interacting with this project.
 
+## Running the tests locally
+
+Moto has a Makefile which has some helpful commands for getting setup. You should be able to run `make init` to install the dependencies and then `make test` to run the tests.
+
 ## Is there a missing feature?
 
 Moto is easier to contribute to than you probably think. There's [a list of which endpoints have been implemented](https://github.com/spulec/moto/blob/master/IMPLEMENTATION_COVERAGE.md) and we invite you to add new endpoints to existing services or to add new services.

Makefile

@@ -10,7 +10,7 @@ endif
 
 init:
 	@python setup.py develop
-	@pip install -r requirements.txt
+	@pip install -r requirements-dev.txt
 
 lint:
 	flake8 moto