Include shared settings, according to official docs

Official docs, found here:
https://intellij-support.jetbrains.com/hc/en-us/articles/206544839 (as
of 13 Aug 2016)

Global/JetBrains.gitignore

@@ -4,9 +4,6 @@
 # User-specific stuff:
 .idea/workspace.xml
 .idea/tasks.xml
-.idea/dictionaries
-.idea/vcs.xml
-.idea/jsLibraryMappings.xml
 
 # Sensitive or high-churn files:
 .idea/dataSources.ids