Yona support social login, Github and Gmail.
It doesn't need to sign up anymore.

This feature was easily developed thanks to "Play Athenticate"
See: https://github.com/joscha/play-authenticate

Suport yona to github migration.
It can be processed at /migration url path.

eg. https://repo.yona.io/migration

Yobi was making public/uploadFiles when it starts, but the directory
looks not to be used.

- any settings in application.user.conf will override application.conf

* num-badge colored to mono (related with #195)
* repositoryURL: font-family, width has adjusted
* issue, board: font-size, line-height of article Id has modified
* milestone: position of legend on list, description on view has modified
* labels on issue list is link to search with label now
* and more trivial changes