Add script to set Japanese locale

Added a script to set Japanese locale for container.

## Usage

```shell
locale-ja.sh
```

## Example in Dockerfile

```dockerfile
FROM quay.io/wantedly/ruby:2.1

ADD <url_for_locale-ja.sh> .
RUN ./locale.sh

ENV LANG ja_JP.UTF-8
ENV LANGUAGE ja_JP:ja
ENV LC_ALL ja_JP.UTF-8
ENV LC_CTYPE ja_JP.UTF-8
```

## Problem

We have to write ENV sentences in Dockerfile because environments variables declared in ShellScript are not set permanently in the container.
> Don’t do RUN apt-get update on a single line. This will cause caching issues if the referenced archive gets updated, which will make your subsequent apt-get install fail without comment.

https://docs.docker.com/articles/dockerfile_best-practices/#run