Spruce up CHANGELOG with links to each PR #
Spruce up CHANGELOG with links to each PR #

Also fix a formatting issue on the most recent release header.
mkfifo/ponyc,boemmels/ponyc,Perelandric/ponyc,Perelandric/ponyc,Perelandric/ponyc,boemmels/ponyc,kulibali/ponyc,CausalityLtd/ponyc,mkfifo/ponyc,Praetonus/ponyc,cquinn/ponyc,Praetonus/ponyc,jemc/ponyc,CausalityLtd/ponyc,kulibali/ponyc,jemc/ponyc,sgebbie/ponyc,mkfifo/ponyc,sgebbie/ponyc,Theodus/ponyc,kulibali/ponyc,jemc/ponyc,boemmels/ponyc,dipinhora/ponyc,mkfifo/ponyc,Theodus/ponyc,Theodus/ponyc,CausalityLtd/ponyc,Praetonus/ponyc,boemmels/ponyc,dipinhora/ponyc,Praetonus/ponyc,boemmels/ponyc,Theodus/ponyc,sgebbie/ponyc,sgebbie/ponyc,ponylang/ponyc,cquinn/ponyc,sgebbie/ponyc,Theodus/ponyc,ponylang/ponyc,kulibali/ponyc,dipinhora/ponyc,Perelandric/ponyc,cquinn/ponyc,mkfifo/ponyc,Perelandric/ponyc,cquinn/ponyc,ponylang/ponyc