Add missing plugin for releasing (#22)

Author: jakipatryk

project/plugins.sbt

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.5.12")
+
 addSbtPlugin("org.jetbrains.scala" % "sbt-ide-settings" % "1.1.1")
 addSbtPlugin("com.earldouglas" % "xsbt-web-plugin" % "4.2.4")