Fix: sbt test throw an java.lang.OutOfMemoryError: PermGen space

Author: witgo <witgo@qq.com>

Closes #773 from witgo/sbt_javaOptions and squashes the following commits:

26c7d38 [witgo] Improve sbt configuration

.rat-excludes

@@ -43,3 +43,8 @@ test.out/*
 .*iml
 service.properties
 db.lck
+build/*
+dist/*
+.*out
+.*ipr
+.*iws

project/SparkBuild.scala

@@ -183,6 +183,7 @@ object SparkBuild extends Build {
     javaOptions in Test += "-Dspark.testing=1",
     javaOptions in Test += "-Dsun.io.serialization.extendedDebugInfo=true",
     javaOptions in Test ++= System.getProperties.filter(_._1 startsWith "spark").map { case (k,v) => s"-D$k=$v" }.toSeq,
+    javaOptions in Test ++= "-Xmx3g -XX:PermSize=128M -XX:MaxNewSize=256m -XX:MaxPermSize=1g".split(" ").toSeq,
     javaOptions += "-Xmx3g",
     // Show full stack trace and duration in test cases.
     testOptions in Test += Tests.Argument("-oDF"),