docs(CONTRIBUTING.md): Added a not about type

It's important that we let people use the GitHub editing interface without being 100% strict about how to name the commit changes. Otherwise, it is basically a barrier to entry and highly discouraging for new people who may just be trying to fix a spelling error. Since it is possible for contributors to edit the commit message before merging it into master, for people who are new to the commit styling system, we should be lenient about minor infractions like forgetting to put docs: in front of a message. 

CF: angular-ui/bootstrap#2635 (comment)

Author: RichardLitt

CONTRIBUTING.md

@@ -54,7 +54,7 @@ For large fixes, please build and test the documentation before submitting the P
 accidentally introduced any layout or formatting issues. You should also make sure that your commit message
 is labeled "docs:" and follows the **Git Commit Guidelines** outlined below.
 
-If you're just making a small change, don't worry about filing an issue first. Use the friendly blue "Improve this doc" button at the top right of the doc page to fork the repository in-place and make a quick change on the fly.
+If you're just making a small change, don't worry about filing an issue first. Use the friendly blue "Improve this doc" button at the top right of the doc page to fork the repository in-place and make a quick change on the fly. When naming the commit, it is advised to still label it according to the commit guidelines below, by starting the commit message with **docs** and referencing the filename. Since this is not obvious and some changes are made on the fly, this is not strictly necessary and we will understand if this isn't done the first few times. 
 
 ## <a name="submit"></a> Submission Guidelines