Make Buffer.transact restore marker ranges on undo/redo of transaction

We no longer need to restore selection ranges before and after
transactions now because selections are based on markers so they go
along for the ride for free. This allows us to delegate directly to
Buffer.transact from EditSession.

src/app/edit-session.coffee

@@ -618,26 +618,11 @@ class EditSession
   # Internal #
   ###
 
-  transact: (fn) ->
-    isNewTransaction = @buffer.transact()
-    oldSelectedRanges = @getSelectedBufferRanges()
-    @pushOperation
-      undo: (editSession) ->
-        editSession?.setSelectedBufferRanges(oldSelectedRanges, preserveFolds: true)
-    if fn
-      result = fn()
-      @commit() if isNewTransaction
-      result
+  transact: (fn) -> @buffer.transact(fn)
 
-  commit: ->
-    newSelectedRanges = @getSelectedBufferRanges()
-    @pushOperation
-      redo: (editSession) ->
-        editSession?.setSelectedBufferRanges(newSelectedRanges, preserveFolds: true)
-    @buffer.commit()
+  commit: -> @buffer.commit()
 
-  abort: ->
-    @buffer.abort()
+  abort: -> @buffer.abort()
 
   ###
   # Public #