Improve Japanese translation (#2376)
Improve Japanese translation (#2376)

ref #2359

- https://github.com/tootsuite/mastodon/pull/2359#discussion_r112838771
- https://github.com/tootsuite/mastodon/pull/2359#discussion_r112838772
- https://github.com/tootsuite/mastodon/pull/2359#discussion_r112838812
- https://github.com/tootsuite/mastodon/pull/2359#discussion_r112838823
- https://github.com/tootsuite/mastodon/pull/2359#discussion_r112838829
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