Update CONTRIBUTING.md
Update CONTRIBUTING.md

Fix issues url
watson-developer-cloud/yourcelebritymatch,M4gn4tor/yourcelebritymatch,HarryAKA/twitter-watson-insights,M4gn4tor/yourcelebritymatch,HarryAKA/twitter-watson-insights,watson-developer-cloud/your-celebrity-match,l4chong/newbullrush,Spatika/yourcelebritymatch,watson-developer-cloud/yourcelebritymatch,l4chong/newbullrush,marge76/tweet-compare,JakePeyser/runkeeper-hashmatch,marge76/tweet-compare,JakePeyser/runkeeper-hashmatch,cemoulto/yourcelebritymatch,Spatika/yourcelebritymatch,cemoulto/yourcelebritymatch,chrismoulton/yourcelebritymatch,chrismoulton/yourcelebritymatch,watson-developer-cloud/your-celebrity-match