chore(docs): Fixes broken link and typo (Hacker0x01#1558)

CONTRIBUTING.md

@@ -5,7 +5,7 @@ Thanks for taking your time to read this. We're thrilled you're reading this bec
 We have a handful of Cucumber features, but most of our testbed consists of RSpec examples. Please write RSpec examples for new code you create.
 
 ## Submitting changes
-Please send a [GitHub Pull Request](https://github.com/Hacker0x01/react-datepicker/pull/new/master) with a clear list of what you've done (read more about [pull requests](http://help.github.com/pull-requests/)). When you send a pull request, we will love you forever if you include a test to cover your changed. We can always use more test coverage. 
+Please send a [GitHub Pull Request](https://github.com/Hacker0x01/react-datepicker/pull/new/master) with a clear list of what you've done (read more about [pull requests](https://help.github.com/articles/about-pull-requests/)). When you send a pull request, we will love you forever if you include a test to cover your changes. We can always use more test coverage.
 Always write a clear log message for your commits. One-line messages are fine for small changes, but bigger changes should look like this:
     $ git commit -m "A summary of the commit
     >