Adding mutation test

Author: rmleon

project/plugins.sbt

@@ -2,4 +2,5 @@ logLevel := Level.Warn
 
 resolvers += "Sonatype OSS Releases" at "https://oss.sonatype.org/service/local/staging/deploy/maven2"
 
-addSbtPlugin("org.scalariform" % "sbt-scalariform" % "1.6.0")
+addSbtPlugin("io.stryker-mutator" % "sbt-stryker4s" % "0.6.1")
+addSbtPlugin("org.scalariform" % "sbt-scalariform" % "1.8.3")