Change from gradle to SBT.

Things were just annoying enough that I went back to SBT.

Hopefully I don't regret this

.gitignore

-# Created by https://www.gitignore.io/api/elm,scala,gradle,intellij+all
+# Created by https://www.gitignore.io/api/elm,scala,sbt,intellij+all
 
 ### Elm ###
 # elm-package generated files
@@ -81,26 +81,24 @@ modules.xml
 .idea/misc.xml
 *.ipr
 
+### SBT ###
+# Simple Build Tool
+# http://www.scala-sbt.org/release/docs/Getting-Started/Directories.html#configuring-version-control
+
+dist/*
+target/
+lib_managed/
+src_managed/
+project/boot/
+project/plugins/project/
+.history
+.cache
+.lib/
+
 ### Scala ###
 *.class
 *.log
 
-### Gradle ###
-.gradle
-/build/
-
-# Ignore Gradle GUI config
-gradle-app.setting
-
-# Avoid ignoring Gradle wrapper jar file (.jar files are usually ignored)
-!gradle-wrapper.jar
-
-# Cache of project
-.gradletasknamecache
-
-# # Work around https://youtrack.jetbrains.com/issue/IDEA-116898
-# gradle/wrapper/gradle-wrapper.properties
-
 
-# End of https://www.gitignore.io/api/elm,scala,gradle,intellij+all
+# End of https://www.gitignore.io/api/elm,scala,sbt,intellij+all