Add basic contributor guideline pointing to HQ URL

For the GitHub API https://github.com/blog/1184-contributing-guidelines

Signed-off-by: Simon Stewart <[email protected]>

Author: nschonni

Diff for: CONTRIBUTING.md

@@ -0,0 +1,8 @@
+#Contributing to Selenium
+Please review the [Getting Involved](http://docs.seleniumhq.org/about/getting-involved.jsp) guide first.
+
+##Creating a PR
+Please read [Contributing Code to Selenium](http://docs.seleniumhq.org/about/getting-involved.jsp#contributing-code-to-selenium).
+
+##Reporting an issue
+Please read [Bug Reports and Feature Requests](http://docs.seleniumhq.org/about/getting-involved.jsp#bug-reports-and-feature-requests)