CHANGELOG: update for 1.5
CHANGELOG: update for 1.5

chambart/merlin,haselwarter/merlin,dra27/merlin,the-lambda-church/merlin,ocaml/merlin,ocaml/merlin,fxfactorial/merlin,rgrinberg/merlin,fxfactorial/merlin,neojski/merlin,ocaml/merlin,haselwarter/merlin,ocaml/merlin,fxfactorial/merlin,chriskonstad/merlin,neojski/merlin,rgrinberg/merlin,chambart/merlin,haselwarter/merlin,dra27/merlin,fxfactorial/merlin,neojski/merlin,dra27/merlin,the-lambda-church/merlin,rgrinberg/merlin,dra27/merlin,rgrinberg/merlin,chambart/merlin,neojski/merlin,the-lambda-church/merlin,haselwarter/merlin,chambart/merlin,chriskonstad/merlin