Fix issue tracker links

Author: wooldridge

CONTRIBUTING.md

@@ -16,11 +16,11 @@ with MarkLogic.
 
 ## <a name="issue"></a> Found an Issue?
 If you find a bug in the source code or a mistake in the documentation, you can help us by
-submitting an issue to our [GitHub Issue Tracker][issue tracker]. Even better 
+submitting an issue to our [GitHub Issue Tracker](https://github.com/marklogic/node-client-api/issues). Even better
 you can submit a Pull Request with a fix for the issue you filed.
 
 ## <a name="feature"></a> Want a Feature?
-You can request a new feature by submitting an issue to our [GitHub Issue Tracker][issue tracker].  If you would like to implement a new feature, first create a new issue and discuss it with one of our project 
+You can request a new feature by submitting an issue to our [GitHub Issue Tracker](https://github.com/marklogic/node-client-api/issues).  If you would like to implement a new feature, first create a new issue and discuss it with one of our project
 maintainers.
 
 ## <a name="submit"></a> Submission Guidelines
@@ -54,7 +54,7 @@ and clone your copy.
 
 All bug fixes and new features go into the `develop` branch.
 
-We ask that you open an issue in the [issue tracker][] and get agreement from at least one of the project maintainers before you start coding.
+We ask that you open an issue in the [issue tracker](https://github.com/marklogic/node-client-api/issues) and get agreement from at least one of the project maintainers before you start coding.
 
 Nothing is more frustrating than seeing your hard work go to waste because your vision does not align with that of a project maintainer.