Update changelog for 1.0.0.
Update changelog for 1.0.0.

ks94/javapoet,ks94/javapoet,DanielSerdyukov/javapoet,auke-/javawriter,studyfordream/javapoet,sitexa/javapoet,ponsonio/javapoet,APaloski/javapoet,rajatguptarg/javapoet,ben-manes/javapoet,gk5885/javawriter,gk5885/javawriter,sormuras/javapoet,square/kotlinpoet,sormuras/javapoet,square/javapoet,ponsonio/javapoet,auke-/javawriter,mumer92/javapoet,APaloski/javapoet,studyfordream/javapoet,mumer92/javapoet,kenzierocks/javapoet,square/kotlinpoet,square/javawriter,eamonnmcmanus/javapoet,kenzierocks/javapoet,eamonnmcmanus/javapoet,sitexa/javapoet,DanielSerdyukov/javapoet,rajatguptarg/javapoet,ben-manes/javapoet