Docs: Add 4.0 changelog

Author: phated

CHANGELOG.md

@@ -1,5 +1,15 @@
 # gulp changelog
 
+## 4.0.0
+
+- removed task dependency graph, everything must be composed using `gulp.series` or `gulp.parallel`
+- removed 3 argument syntax for `gulp.task` due to task dependency graph being removed.
+- added `gulp.series` and `gulp.parallel` methods for composing tasks.
+- added single argument syntax for `gulp.task` which allows a named function to be used as the name of the task and task function.
+- added `gulp.tree` method for retrieving the task tree. Pass `{ deep: true }` for an `archy` compatible node list.
+- added `--verify` flag to check the dependencies in package.json against the plugin blacklist.
+- added `gulp.registry` for setting custom registries.
+
 ## 3.9.1
 
 - update interpret to 1.0.0 (support for babel-register)