Fix typo
Modified target platform (#315, #323).
Release notes for version 0.5.3 (#323).
Fixed #329 (#323).

runtime.core.Result tend to misunderstand that cannot add multiple
objects.
Merge remote-tracking branch 'cocoatomo/patch-7' into wip/issue/337
(#337)
Fix a valid CoGroup operator method (#338)
Merge remote-tracking branch 'private/issue/323-M3' into 0.5-develop
Merge remote-tracking branch 'private/issue/329' into 0.5-develop
Merge remote-tracking branch 'private/issue/337' into 0.5-develop
Merge remote-tracking branch 'private/issue/338' into 0.5-develop