use specs2-core instead of specs2. update specs2 2.4.4
Merge pull request #284 from xuwei-k/specs2-core

use specs2-core instead of specs2. update specs2 2.4.4
fix issue 285. don't repeat default values
Merge pull request #287 from xuwei-k/do-not-repeat-default-value

fix issue 285. don't repeat default values
Added gitter badge
Merge pull request #291 from scalikejdbc/gitter-badge

Added gitter badge
Add Gitter badge for Japanese