Format the style guide

Author: mr-c

CONTRIBUTING.md

@@ -1,8 +1,8 @@
 Style guide:
-PEP-8
-Python 2.7 + Python 3.5+ compatible code
-PEP-484 type hints, in comments for Python 2.7 compatability
-Vertically align the type hints in function definitions
+- PEP-8
+-Python 2.7 + Python 3.5+ compatible code
+- PEP-484 type hints, in comments for Python 2.7 compatability
+- Vertically align the type hints in function definitions
 
 In order to contribute to the development of ``cwltool``, you need to install cwltool from source (preferably in a virtual environment):
 Here's a rough guide (improvements are welcome!)