Update guidelines

CONTRIBUTING.md

@@ -1,13 +1,15 @@
 #Contributing Guidelines
 
-Thank you for your contributing! My requests are few things. Please read below.
+Thanks for taking the time to contribute!
+
+The following is a set of guidelines for contributing to zulip-electron. These are just guidelines, not rules, use your best judgment and feel free to propose changes to this document in a pull request.
 
 ## Getting Started
 
 Zulip-Desktop app is built on top of [Electron](http://electron.atom.io/). If you are new to Electron please head over to [this](http://jlord.us/essential-electron/) great article.
 
 ## Issue
-Thank you for feedback. When you report a problem, please pay attention to following points.
+Ensure the bug was not already reported by searching on GitHub under [Issues](https://github.com/zulip/zulip-electron/issues). If you're unable to find an open issue addressing the problem, [open a new one](https://github.com/zulip/zulip-electron/issues/new). Please pay attention to following points while opening an issue.
 
 ### Does it happen on web browsers? (especially Chrome)
 Zulip-Desktop is based on Electron, which integrates the Chrome engine within a standalone application.
@@ -25,10 +27,11 @@ For example:
 * Zulip-Desktop version
 
 
-## Pull request
-Pull requests are welcome. Thank you for your great work!
+## Pull Requests
+Pull Requests are welcome. 
 
-1. When you edit the code, please run npm run test to check formatting of your code before git commit.
-2. In the description of your pull request, please include:
+1. When you edit the code, please run `npm run test` to check formatting of your code before git commit.
+2. Ensure the PR description clearly describes the problem and solution. It should include:
    * Operating System version on which you tested
    * Zulip-Desktop version on which you tested
+   * The relevant issue number if applicable