Clarify setting PYTHONPATH in dev environment (Yelp#374)

* Clarify setting PYTHONPATH in dev environment

Updates CONTRIBUTING.md with details about why PYTHONPATH needs to be set in one's dev environment. Explains the consequences of not doing so.

* Remove random bullet point from top of README

CONTRIBUTING.md

@@ -118,6 +118,13 @@ executing:
 PYTHONPATH=`pwd` python detect_secrets/main.py --version
 ```
 
+Note that without `PYTHONPATH` set, Python will not be able to resolve imports
+within this repo. Particularly if you have the `detect-secrets` package
+installed in your environment, Python may resolve module imports from the
+installed `detect-secrets` package instead of from within the repo where you're
+developing. To avoid this, ensure `PYTHONPATH` is set in your developer
+environment and includes the path to the whitewater-detect-secrets repo.
+
 
 ## Running Tests
 

README.md

@@ -1,4 +1,4 @@
-- [![Build Status](https://travis.ibm.com/Whitewater/whitewater-detect-secrets.svg?token=tSTYkwXezbKBusqJ3V4L&branch=master)](https://travis.ibm.com/Whitewater/whitewater-detect-secrets)
+[![Build Status](https://travis.ibm.com/Whitewater/whitewater-detect-secrets.svg?token=tSTYkwXezbKBusqJ3V4L&branch=master)](https://travis.ibm.com/Whitewater/whitewater-detect-secrets)
 
 # Whitewater Detect Secrets