fix contributing bug

Author: lukepolson

CONTRIBUTING.md

@@ -10,7 +10,7 @@ First off, thanks for your interest in contributing! There are many potential op
 **New Features**
 
 The recommended method of contributing is as follows:
-1. Create an issue on the (issues page)[https://github.com/lukepolson/SPECTPSFToolbox/issues]
+1. Create an issue on the [issues page](https://github.com/lukepolson/SPECTPSFToolbox/issues)
 2. Fork the repository to your own account
 3. Fix issue and push changes to your own fork on GitHub
 4. Create a pull request from your fork (whatever branch you worked on) to the development branch in the main repository,