When font size changes, correctly adjust scrollable height

This requires updating the padding of the rendered lines and then adjusting the vertical scrollbar content height before updating any of the rendered lines. This fixes (hopefully all of) the rendering issues when adjusting the font size.

src/app/editor.coffee

@@ -572,6 +572,8 @@ class Editor extends View
     if fontSize?
       @css('font-size', fontSize + 'px')
       @calculateDimensions()
+      @updatePaddingOfRenderedLines()
+      @handleScrollHeightChange()
       @updateCursorViews()
       @updateRenderedLines()