Merge pull request #281 from http4s/update/sbt-http4s-org-0.18.0

Update sbt-http4s-org to 0.18.0

Author: danicheg

Diff for: project/plugins.sbt

@@ -1,4 +1,4 @@
-addSbtPlugin("org.http4s" % "sbt-http4s-org" % "0.17.7")
+addSbtPlugin("org.http4s" % "sbt-http4s-org" % "0.18.0")
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.17.0")
 addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.4.17")
 addSbtPlugin("org.portable-scala" % "sbt-scala-native-crossproject" % "1.3.2")