[issue-1276] update CHANGELOG.md for 2.0.0 release
[issue-1276] update CHANGELOG.md for 2.0.0 release

sinatra/sinatra,sinatra/sinatra,JonMidhir/sinatra,ryanshaw/sinatra,ryanshaw/sinatra,jkowens/sinatra,JonMidhir/sinatra,jkowens/sinatra,JonMidhir/sinatra,jkowens/sinatra