adding describeTable partial support for fakedynamo

Hello @x-ma, 

Please review the following commits I made in branch 'giannic-tables'.

0d44c39e475e6fd5889dc7daba206edf9aa8d68f (2014-04-15 13:36:54 -0700)
adding describeTable partial support for fakedynamo

R=@x-ma