Fix py.test run in documentation (exercism#334)

Just add '\n' between `cd` and `py.test` commands

Author: puzan

docs/TESTS.md

@@ -70,15 +70,17 @@ py.test --ff bob_test.py
 ### Running All Tests for All Exercises
 
 ```bash
-cd exercism/python/ py.test
+cd exercism/python/
+py.test
 ```
 
 ## Recommended Workflow
 
 We recommend you run this command while working on exercises.
 
 ```bash
-cd exercism/python/bob py.test -x --ff bob_test.py
+cd exercism/python/bob
+py.test -x --ff bob_test.py
 ```
 
 ## PDB