Updated CONTRIBUTING.md file to point at dev sites insead of GitHub wiki sites. (#722)
Updated CONTRIBUTING.md file to point at dev sites insead of GitHub wiki sites. (#722)

* Updated CONTRIBUTING.md file to point at dev sites insead of GitHub wiki sites.

* Added changes based on code review for #679.
google/blockly-samples,google/blockly-samples,google/blockly-samples,google/blockly-samples