Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -4,12 +4,12 @@ We welcome feature proposals and improvements to the library from anyone. If you
 discussion, or get in touch with Jim Rybarski via email at jim@rybarski.com, or on Twitter at [@jimrybarski](https://twitter.com/jimrybarski). If you already wrote some code or made changes, simply open a pull
 request.
 
-# Easy Tasks for Beginners
+## Easy Tasks for Beginners
 
 There are issues labeled `easy` which are small but useful tasks that are designed for people who are new to open source projects. If you'd like to work on one, feel free to just
 take one on, or get in touch if you need help.
 
-# Running and Writing Tests
+## Running and Writing Tests
 
 Unit tests can be run with the commands `python3.4 test.py` and `python2.7 test.py`. The test finder will automatically locate any tests in the `tests` directory. Test classes
 must inherit from `unittest.TestCase` and tests will only be run if the function name starts with `test`. If you've built the Docker image, you can also run unit tests with
@@ -18,11 +18,11 @@ must inherit from `unittest.TestCase` and tests will only be run if the function
 There are also functional tests that work with real ND2s to make sure the code actually works with a wide variety of files. We hope to someday put these into a continuous integration
 system so everyone can benefit, but for now, they will just be manually run by the maintainer of this library before merging in any contributions.
 
-# Contributing Your ND2 files
+## Contributing Your ND2 files
 
 We always appreciate more ND2s, as they help us find corner cases. Please get in touch using any of the means listed at the top of this page if you'd like to send one in.
 
-# Docker and Makefile Commands
+## Docker and Makefile Commands
 
 A Dockerfile is included to allow testing in a consistent environment. `make build` will build the image for you. Due to the large number of packages that it installs, it often
 fails due to a problem with the Debian servers - just try again if this happens. Once that's complete, you can run `make py2` or `make py3` to enter into a Python interpreter in