Make .gitignore minimal, don't commit .idea and build/ to version control

.gitignore

@@ -1,94 +1,11 @@
-
-
-# Created by https://www.gitignore.io/api/java,intellij
-
-### Intellij ###
-# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio and Webstorm
-# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
-
-# User-specific stuff:
-.idea/**/workspace.xml
-.idea/**/tasks.xml
-.idea/dictionaries
-
-# Sensitive or high-churn files:
-.idea/**/dataSources/
-.idea/**/dataSources.ids
-.idea/**/dataSources.xml
-.idea/**/dataSources.local.xml
-.idea/**/sqlDataSources.xml
-.idea/**/dynamic.xml
-.idea/**/uiDesigner.xml
-
-# Gradle:
-.idea/**/gradle.xml
-.idea/**/libraries
-
-# CMake
-cmake-build-debug/
-
-# Mongo Explorer plugin:
-.idea/**/mongoSettings.xml
-
-## File-based project format:
-*.iws
-
-## Plugin-specific files:
+# Gradle
+build/
+gradle.properties
+.gradle/
 
 # IntelliJ
 /out/
-
-# mpeltonen/sbt-idea plugin
-.idea_modules/
-
-# JIRA plugin
-atlassian-ide-plugin.xml
-
-# Cursive Clojure plugin
-.idea/replstate.xml
-
-# Crashlytics plugin (for Android Studio and IntelliJ)
-com_crashlytics_export_strings.xml
-crashlytics.properties
-crashlytics-build.properties
-fabric.properties
-
-### Intellij Patch ###
-# Comment Reason: https://github.com/joeblau/gitignore.io/issues/186#issuecomment-215987721
-
-# *.iml
-# modules.xml
-# .idea/misc.xml
-# *.ipr
-
-# Sonarlint plugin
-.idea/sonarlint
-
-### Java ###
-# Compiled class file
-*.class
-
-# Log file
-*.log
-
-# BlueJ files
-*.ctxt
-
-# Mobile Tools for Java (J2ME)
-.mtj.tmp/
-
-# Package Files #
-*.jar
-*.war
-*.ear
-*.zip
-*.tar.gz
-*.rar
-
-# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
-hs_err_pid*
-
-# End of https://www.gitignore.io/api/java,intellij
-
-gradle.properties
-.gradle
+.idea/
+*.iml
+*.ipr
+*.iws