Tweaks all japanese text in gh-pages

Hi @mariten!
I made Japanese text more natural :santa:
You can see the preview of this PR at here: http://watilde.github.io/kanatools-java/ja/

Thanks :christmas_tree:
This is a good change, but I'm just curious:
You've changed the two `<p>` blocks to be a single `<p>` block with a new-line inside of it.  Was that because:
1. It looked better from a UI design perspective (デザイン的な観点から)? Or
2. The look of the Japanese is better that way (日本語の文字の見た目そのものがより綺麗)?