Add an IDEA template to cover all related IDEs

Global/IDEA.gitignore

+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode
+
+## Directory-based project format
+.idea/
+# if you remove the above rule, at least ignore user-specific stuff:
+# .idea/workspace.xml
+# .idea/dataSources.ids
+# .idea/dataSources.xml
+# .idea/sqlDataSources.xml
+# .idea/dynamic.xml
+
+## File-based project format
+*.ipr
+*.iws
+*.iml