Implement a data importer

Hello @nicks, @dpup, 

Please review the following commits I made in branch 'xiao-data-import'.

420cf3bf38ead5b9e4e607851b3cd2b7161cd818 (2014-02-21 22:35:59 -0800)
Implement a data importer

ca5de032af362a0fc946a89e806549f83dc747b8 (2014-02-21 15:11:20 -0800)
Upgrade to the 2014-01-08 version of AWS DynamoDB Local

R=@nicks
R=@dpup