Bumping version to 1.9.0 and generate changelog

Author: FishtownBuildBot

.bumpversion.cfg

@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 1.9.0rc2
+current_version = 1.9.0
 parse = (?P<major>[\d]+) # major version number
 	\.(?P<minor>[\d]+) # minor version number
 	\.(?P<patch>[\d]+) # patch version number