Translate Japanese Tutorial for sbt 0.13

Based on [latest English tutorial](https://github.com/sbt/website/tree/408a3f416fe0893ca7d2e710b130613e429c28ae/src/tutorial), I fixed Japanese tutorial for sbt0.13.
There are many changes, if possible, plz check them.
原文が間違ってる？のかもしれないけど、`build.sbt` 内でも、`val`や`def`は空白行で区切らずに書けたような