Doc tweaks

* Minor Markdown tweaks
* Fix a few typos
* Fix the release-it URL
* Switch to shields.io for the Travis CI badge too

contributing.md

@@ -3,6 +3,7 @@
 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.
 
@@ -12,28 +13,36 @@ detailed information about how the various folders and files in this project are
   - <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
-    ````
+
+    ```sh
+    git checkout -b BRANCH_NAME
+    ```
+
     If you get an error, you may need to fetch first, by using
-    ````
-    $ git remote update && git fetch
-    ````
+
+    ```sh
+    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'
-    ````
+
+    ```sh
+    git commit -am 'Add some fooBar'
+    ```
+
 - Push to the branch
   - Example:
-    ````
-    $ git push origin BRANCH_NAME
-    ````
+
+    ```sh
+    git push origin BRANCH_NAME
+    ```
+
 - Make a pull request
-  - Make sure you send the PR to the <code>BRANCH_NAM</code> branch
+  - Make sure you send the PR to the `BRANCH_NAME` branch
 
 If you follow these instructions, your Pull Request will land safely!