title: ag grid sizeColumnsToFit for columns not working
body: <p>I have used ag-grid ng2 and trying to apply sizeColumnsToFit. 
      For example: If there are 4 columns then it should be automatically resized and fit to the width of grid. 
      gridOptions.api.sizeColumnsToFit() not working.</p>
  
  <pre><code>var gridOptions = {
      columnDefs: columnDefs,
      rowData: null,
      enableColResize: true
  };
  
  this.columnDefs = [
       {headerName: "Age", field: "age", width: 90, minWidth: 50, maxWidth: 100},
      {headerName: "Country", field: "country", width: 120},
      {headerName: "Year", field: "year", width: 90},
      {headerName: "Date", field: "date", width: 110}
  
  
      ];
  
   gridOptions.api.sizeColumnsToFit();
  </code></pre>