Remove Yomitan redirections for search keys with trivial kana differences

[stephenmk]

Related issue: #78

When scanning 黒ヤギ, Yomitan automatically converts to hiragana and searches for both "黒ヤギ" and "黒やぎ". This causes an undesirable "redirected from 黒やぎ" message to appear under the heading for "黒ヤギ" even though no such redirection was actually intended.

I need to remove these automatic redirections for these sorts of trivial conversions that are already handled by Yomitan.

[stephenmk]

This will more-or-less be fixed in the next version of jitendex. I've disabled the redirects for the trivial all-hiragana and all-katakana conversions. There are probably some not-so-trivial conversions I could also disable since Yomitan is able to automatically redirect something like くせー to 臭い. But I guess this is good enough for now.

This will also prevent the ugly bug described here from occurring for queries like ホシ.