Shim rowsPerPage property on Editor instances

Several packages were relying on a raw property rather than the getter
method. This isn't really supported, but may as well keep them working.

src/text-editor.coffee

@@ -3527,6 +3527,10 @@ class TextEditor extends Model
     else
       1
 
+  Object.defineProperty(@prototype, 'rowsPerPage', {
+    get: -> @getRowsPerPage()
+  })
+
   ###
   Section: Config
   ###