Add contributing guidelines, and a page explaining the repo's file and folder structure.

contributing.md

@@ -0,0 +1,39 @@
+# Contributing Guide
+
+- Contributing to Hosts is easy. This document shows you how to get started
+
+## General
+- The [Codebase Structure](https://github.com/StevenBlack/hosts/blob/master/codebase_structure.md) has
+detailed information about how the various folders and files in this project are structured.
+
+## Submitting changes
+
+- Fork the repo
+  - <https://github.com/StevenBlack/hosts/fork>
+- Check out a new branch based and name it to what you intend to do:
+  - Example:
+    ````
+    $ git checkout -b BRANCH_NAME
+    ````
+    If you get an error, you may need to fetch first, by using
+    ````
+    $ git remote update && git fetch
+    ````
+  - Use one branch per fix / feature
+- Commit your changes
+  - Please provide a git message that explains what you've done
+  - Please make sure your commits follow the [conventions](https://gist.github.com/robertpainsi/b632364184e70900af4ab688decf6f53#file-commit-message-guidelines-md)
+  - Commit to the forked repository
+  - Example:
+    ````
+    $ git commit -am 'Add some fooBar'
+    ````
+- Push to the branch
+  - Example:
+    ````
+    $ git push origin BRANCH_NAME
+    ````
+- Make a pull request
+  - Make sure you send the PR to the <code>BRANCH_NAME</code> branch
+
+If you follow these instructions, your Pull Request will land safely!