Update contributing.md

CONTRIBUTING.md

@@ -4,6 +4,8 @@ Thanks for your contributions!
 
 ## Submit bug reports or feature requests
 
+Please discuss the changes with us ahead of time to ensure they will be merged.
+
 ### Submit pull requests
  * [Fork](https://github.com/invoiceninja/invoiceninja#fork-destination-box) the [Invoice Ninja repository](https://github.com/invoiceninja/invoiceninja)
  * Create a new branch with the name `#issue_number-Short-description`
@@ -11,7 +13,7 @@ Thanks for your contributions!
  * Make your changes and commit
  * Check if your branch is still in sync with the repositorys **`develop`** branch
    * _Read:_ [Syncing a fork](https://help.github.com/articles/syncing-a-fork/)
-   * _Also read:_ [How to rebase a pull request](https://github.com/edx/edx-platform/wiki/How-to-Rebase-a-Pull-Request) 
+   * _Also read:_ [How to rebase a pull request](https://github.com/edx/edx-platform/wiki/How-to-Rebase-a-Pull-Request)
  * Push your branch and create a PR against the Invoice Ninja **`develop`** branch
  * Update the [Changelog](CHANGELOG.md)
 
@@ -21,7 +23,7 @@ To make the contribution process nice and easy for anyone, please follow some ru
 to give a more detailed explanation.
  * Only one feature/bugfix per issue. If you want to submit more, create multiple issues.
  * Only one feature/bugfix per PR(pull request). Split more changes into multiple PRs.
- 
+
 #### Coding Style
 Try to follow the [PSR-2 guidlines](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md)
 
@@ -29,7 +31,7 @@ _Example styling:_
 ```php
 /**
  * Gets a preview of the email
- * 
+ *
  * @param TemplateService $templateService
  *
  * @return \Illuminate\Http\Response