Multibyte character support for Exporter::shortenedExport()

Currently, long multibyte string are garbled with `Exporter::shortenedExport()` as the following:

![garbled-string](https://cloud.githubusercontent.com/assets/52985/5469192/334fd2ae-861c-11e4-8cc3-d93e1e5f1375.png)

This PR provides multibyte character support for `Exporter::shortenedExport()`.

BTW, the test data is [the Iroha](http://en.wikipedia.org/wiki/Iroha) as [hiragana](http://en.wikipedia.org/wiki/Hiragana).