title: pandas value_counts( ) not in descending order
body: <p>There is a dataframe,df</p>
  
  <pre><code>Index              Date               Name         Category
   0            2017-08-09              ABC-SAP       1
   1            2017-08-09              CDE-WAS       2
   2            2017-08-10              DEF           3
   3            2017-08-11              DEF           3
   4            2017-08-11              CDE-WAS       2
   5            2017-08-11              CDE-WAS       2
  </code></pre>
  
  <p>I executed this code:</p>
  
  <pre><code>df2=pd.DataFrame(df, columns= ['Name','Category'])
  df2= df['Name'].groupby(df['Category']).value_counts()
  print(df2)
  </code></pre>
  
  <p>Then I get:</p>
  
  <pre><code> Index             Name
   (1,ABC-SAP)       1              
   (2,CDE-WAS)       3                         
   (3,DEF)           2             
  </code></pre>
  
  <p>The value.counts( ) does not return a descending order on the NAME column. I really want to have it in descending order from highest to lowest count. Any way of doing it?</p>