bump version to 1.7.0

Author: takezoe

build.sbt

@@ -1,7 +1,7 @@
 organization     := "gitbucket"
 name             := "gitbucket-pages-plugin"
 scalaVersion     := "2.12.4"
-version          := "1.6.0"
+version          := "1.7.0"
 gitbucketVersion := "4.23.0"
 scalacOptions    := Seq("-unchecked", "-deprecation", "-encoding", "utf8", "-feature")