Implement d3w

NumericPrefix now has a .select() method that calls select multiple
times on its operand. Editor.selectToPosition modified to extend
existing selections, and only create a new one if needed. This allows
repetition of a motion's select method to expand the selection.

spec/atom/vim-mode-spec.coffee

@@ -68,6 +68,16 @@ describe "VimMode", ->
           expect(editor.buffer.getText()).toBe "abefg"
           expect(editor.getCursor()).toEqual {column: 2, row: 0}
 
+          editor.buffer.setText("one two three four")
+          editor.setCursor(column: 0, row: 0)
+
+          editor.trigger keydownEvent('d')
+          editor.trigger keydownEvent('3')
+          editor.trigger keydownEvent('w')
+
+          expect(editor.buffer.getText()).toBe "four"
+          expect(editor.getCursor()).toEqual {column: 0, row: 0}
+
     describe "basic motion bindings", ->
       beforeEach ->
         editor.buffer.setText("12345\nabcde\nABCDE")

src/atom/editor.coffee

@@ -59,8 +59,9 @@ class Editor extends Template
       @aceEditor.navigateTo(row, column)
 
     selectToPosition: (position) ->
-      { row, column } = @getCursor()
-      @aceEditor.selection.setSelectionAnchor(row, column)
+      if @aceEditor.selection.isEmpty()
+        { row, column } = @getCursor()
+        @aceEditor.selection.setSelectionAnchor(row, column)
       @aceEditor.moveCursorToPosition(position)
 
     delete: ->

src/atom/vim-mode-operators.coffee

@@ -22,6 +22,9 @@ module.exports =
     execute: (editor) ->
       _.times @count, => @operatorToRepeat.execute(editor)
 
+    select: (editor) ->
+      _.times @count, => @operatorToRepeat.select(editor)
+
   Delete: class
     complete: null
     motion: null