Add testing instructions to the README

Author: embs

README.md

@@ -114,3 +114,11 @@ Gitless's code so that your edits are consistent with the codebase
 - Finally, if you don't want [Travis](
     https://travis-ci.org/sdg-mit/gitless "Travis") to
 be mad at you, check that tests pass in Python 2.7 and 3.2+
+
+Tests can be run with
+
+```
+pip install nose
+nosetests # run tests other than end-to-end tests
+nosetests ./gitless/tests/test_e2e.py # run end-to-end tests
+```