Allow buffer marker head and tail positions to be manipulated

src/app/buffer-marker.coffee

@@ -33,6 +33,14 @@ class BufferMarker
 
   getTailPosition: -> @tailPosition
 
+  setHeadPosition: (headPosition, options={}) ->
+    @headPosition = Point.fromObject(headPosition)
+    @headPosition = @buffer.clipPosition(@headPosition) if options.clip ? true
+
+  setTailPosition: (tailPosition, options={}) ->
+    @tailPosition = Point.fromObject(tailPosition)
+    @tailPosition = @buffer.clipPosition(@tailPosition) if options.clip ? true
+
   getStartPosition: ->
     @getRange().start
 
@@ -79,17 +87,6 @@ class BufferMarker
 
     [newRow, newColumn]
 
-  setTailPosition: (tailPosition, options={}) ->
-    @tailPosition = Point.fromObject(tailPosition)
-    @tailPosition = @buffer.clipPosition(@tailPosition) if options.clip ? true
-
-  setHeadPosition: (headPosition, options={}) ->
-    @headPosition = Point.fromObject(headPosition)
-    @headPosition = @buffer.clipPosition(@headPosition) if options.clip ? true
-
-  getPosition: ->
-    @position
-
   invalidate: (preserve) ->
     delete @buffer.validMarkers[@id]
     @buffer.invalidMarkers[@id] = this

src/app/buffer.coffee

@@ -283,15 +283,24 @@ class Buffer
   markPosition: (position, options) ->
     @markRange([position, position], _.defaults({noTail: true}, options))
 
-  getMarkerPosition: (id) ->
-    @getMarkerHeadPosition(id)
+  getMarkerPosition: (args...) ->
+    @getMarkerHeadPosition(args...)
+
+  setMarkerPosition: (args...) ->
+    @setMarkerHeadPosition(args...)
 
   getMarkerHeadPosition: (id) ->
     @validMarkers[id]?.getHeadPosition()
 
+  setMarkerHeadPosition: (id, position, options) ->
+    @validMarkers[id]?.setHeadPosition(position)
+
   getMarkerTailPosition: (id) ->
     @validMarkers[id]?.getTailPosition()
 
+  setMarkerTailPosition: (id, position, options) ->
+    @validMarkers[id]?.setTailPosition(position)
+
   getMarkerRange: (id) ->
     @validMarkers[id]?.getRange()