added links to contributing guide and code of conduct

Author: chrisgorgo

README.rst

@@ -90,3 +90,8 @@ To participate in the Nipype development related discussions please use the foll
 
 Please add *[nipype]* to the subject line when posting on the mailing list.
 
+Contributing to the project
+---------------------------
+
+If you'd like to contribute to the project please read our [guidelines](CONTRIBUTING.md). Please also read through our [code of conduct](CODE_OF_CONDUCT.md).
+