Update features.md

Trimmed line 2 for clarity and moved sections and added headings

docs/contributing/features.md

 # New Features
 
-We review contributions of new features (e.g., new packages, new scripts, new flags) to the core stacks in an attempt to balance the value of the images to the Jupyter community with the cost of maintaining the images over time. Roughly speaking, we think about the following when considering additions:
+Thank you for contributing to docker-stacks! We review pull requests of new features (e.g., new packages, new scripts, new flags) to balance the value of the images to the Jupyter community with the cost of maintaining the images over time.
+
+## Suggesting a New Feature
+
+Please follow the process below to suggest a new feature for inclusion in one of the core stacks:
+
+1. [Open a GitHub issue](https://github.com/jupyter/docker-stacks/issues) describing the feature you'd like to contribute.
+2. Discuss with the maintainers whether the addition makes sense in [one of the core stacks](../using/selecting.html#Core-Stacks), as a [recipe in the documentation](recipes.html), as a [community stack](stacks.html), or as something else entirely.
+
+## Selection Criteria
+
+Roughly speaking, we evaluate new features based on the following criteria:
 
 * **Usefulness to Jupyter users**: Is the feature generally applicable across domains? Does it work with Jupyter Notebook, JupyterLab, JupyterHub, etc.?
 * **Fit with the image purpose**: Does the feature match the theme of the stack in which it will be added? Would it fit better in a new, community stack?
@@ -8,17 +19,15 @@ We review contributions of new features (e.g., new packages, new scripts, new fl
 * **Impact on image metrics**: How many bytes does the feature and its dependencies add to the image(s)? How many minutes do they add to the build time?
 * **Ability to support the addition**: Can existing maintainers answer user questions and address future build issues? Are the contributors interested in helping with long-term maintenance? Can we write tests to ensure the feature continues to work over time?
 
-Please follow the process below to suggest a new feature for inclusion in one of the core stacks:
-
-1. [Open a GitHub issue](https://github.com/jupyter/docker-stacks/issues) describing the feature you'd like to contribute.
-2. Discuss with the maintainers whether the addition makes sense in [one of the core stacks](../using/selecting.html#Core-Stacks), as a [recipe in the documentation](recipes.html), as a [community stack](stacks.html), or as something else entirely.
+## Submitting a Pull Request
 
 If there's agreement that the feature belongs in one or more of the core stacks:
 
 1. Implement the feature in a local clone of the `jupyter/docker-stacks` project.
-2. Try to build the image locally (`make image/somestack-notebook`) before submitting a pull request.
-    * Building the image locally gives you a shorter debugging cycle than waiting for [Travis CI](http://travis-ci.org/) to build your changes.
-    * Building locally also takes some load off of Travis CI which graciously provides free build services for open source projects like this one.
+2. Please build the image locally before submitting a pull request. Building the image locally shortens the debugging cycle by taking some load off [Travis CI](http://travis-ci.org/), which graciously provides free build services for open source projects like this one.  If you use `make`, call:
+```
+make image/somestack-notebook
+```
 3. [Submit a pull request](https://github.com/PointCloudLibrary/pcl/wiki/A-step-by-step-guide-on-preparing-and-submitting-a-pull-request) (PR) with your changes.
 4. Watch for Travis to report a build success or failure for your PR on GitHub.
 5. Discuss changes with the maintainers and address any build issues.