Add run rubocop to contributing.md

CONTRIBUTING.md

@@ -2,7 +2,7 @@
 
 1. [Fork the repo](https://help.github.com/articles/fork-a-repo/).
 2. Clone your repo.
-    
+
     ```
     git clone git@github.com:USERNAME/planner.git
     cd planner
@@ -16,23 +16,27 @@
     rails server
     ```
 
-4. Have a look around to get a feel for the app. 
-5. Run the tests. We only take pull requests with passing tests, and it's great to confirm that you have a clean slate. 
+4. Have a look around to get a feel for the app.
+5. Run the tests. We only take pull requests with passing tests, and it's great to confirm that you have a clean slate.
 
     ```
     rake
     ```
 
 6. Add a test for your change - unless you are refactoring or adjusting styles and documentation. If you are adding any functionality or fixing a bug, we need a test!
 7. Implement your change and ensure all the tests pass.
-8. Commit, with a meaningful & descriptive message - this is very important!
+8. Run Rubocop to ensure you are complying with the Ruby style guide. Refer to (https://rubocop.readthedocs.io/en/latest/) for cops/violation details.
+    ```
+    rubocop
+    ```
+9. Commit, with a meaningful & descriptive message - this is very important!
 
     ```
     git commit -m "Title for your commit" -m "A little more explanation"
     ```
 
-9. Push to your fork and [open a pull request on Github](https://help.github.com/articles/creating-a-pull-request/) to the upstream repository.
-10. Wait for comments and feedback - we usually get back super fast!
+10. Push to your fork and [open a pull request on Github](https://help.github.com/articles/creating-a-pull-request/) to the upstream repository.
+11. Wait for comments and feedback - we usually get back super fast!
 
 Syntax guidelines: