Add notes to the README about Bandit on Python 3.4

Change-Id: I6cc420898fc5654486c5b57aca0e362d9d5a5ce8

README.md

@@ -23,6 +23,8 @@ Bandit is distributed on PyPI.  The best way to install it is with pip:
 ***Install Bandit:***
 
     pip install bandit
+    # Or, if you're working with a Python 3 project
+    pip3.4 install bandit
 
 ***Run Bandit:***
 
@@ -170,9 +172,28 @@ You can test any changes with tox:
     pip install tox
     tox -e pep8
     tox -e py27
+    tox -e py34
     tox -e cover
 
 
+Under Which Version of Python Should I Install Bandit?
+------------------------------------------------------
+The answer to this question depends on the project(s) you will be running
+Bandit against. If your project is only compatible with Python 2.7, you
+should install Bandit to run under Python 2.7. If your project is only
+compatible with Python 3.4, then use 3.4. If your project supports both, you
+*could* run Bandit with both versions but you don't have to.
+
+Bandit uses the `ast` module from Python's standard library in order to
+analyze your Python code. The `ast` module is only able to parse Python code
+that is valid in the version of the interpreter from which it is imported. In
+other words, if you try to use Python 2.7's `ast` module to parse code written
+for 3.4 that uses, for example, `yield from` with asyncio, then you'll have
+syntax errors that will prevent Bandit from working properly. Alternatively,
+if you are relying on 2.7's octal notation of `0777` then you'll have a syntax
+error if you run Bandit on 3.4.
+
+
 References
 ==========