Adding Japanese language mo file generated by Poedit.

Adding Japanese mo file, named according to the textdomain name configured in wp-bitly.php.
Your template file "wp-bitly.po" might need to be renamed as wpbitly.po (without dash).

Below is the screenshot on my WordPress with this mo file.

![wp-bit ly_with_ja mo_201301](https://f.cloud.github.com/assets/1251352/43513/8c58cde2-568a-11e2-9d2e-de8c022d9414.png)