Pandoc output header style

[noamross]

Right now, when I produce a pandoc table with column headers, I get:

----------- ------------------
  **Age**     **Length(mm)**  
     1              0         
     2             130        
     3             210        
     4             240        
     5             270        
     6             300        
     7             330        
     8             360        
----------- ------------------

However, I am trying to get headers can recognize, which are this style:

 Age         **Length(mm)**  
----------- ------------------

     1              0         
     2             130        
     3             210        
     4             240        
     5             270        
     6             300        
     7             330        
     8             360        
----------- ------------------

Is this a current option? If so, it is not documented. Otherwise I suggest this become the default pandoc output. Thanks.