title: Extjs gridpanel doesn't expand horizontally within a tabPanel
body: <p>Each of my 3 Extjs gridpanels do not expand horizontally within a tabPanel.</p>
  
  <p>The each grid's properties:</p>
  
  <pre><code>  id: grid_id,
    ds: ds,
    cm: cm,
    loadMask:      true,
    view:          grouping_view,
    plugins:       [expander, filters],
    stateId:       which + '-grid-stateId',
    stateful:      true,
    stateEvents:   ['datachanged', 'columnresize', 'columnmove', 'sortchange', 'columnvisible', 'columnsort', 'hide', 'show', 'expand', 'collapse'],
    selModel:      checkbox,
    // height:        400,
    width:         GRID_WIDTH,
    defaults:      {autoHeight: true},
    autoHeight:    true,
    collapsible:   false,
    animCollapse:  false,
    layout:        'fit',
  </code></pre>
  
  <p>TabPanel's properties:</p>
  
  <pre><code>  id:         'tab_panel',
    renderTo:   'tabs',
    activeTab:  0,
    enableTabScroll:  true,
    defaults:   {autoScroll:true, authHeight:true},
    plugins:    new Ext.ux.TabCloseMenu(),
    width:      GRID_WIDTH + 2,
    autoHeight: true,
    items: [       // put items in tabpanel like this. adding via method call forces them to render/load befire user clicks on them
       owned_grid,
       managed_grid,
       subscribed_grid
    ],
  </code></pre>