Bump package to 0.3.1 so we can use the MultiplexingCache

Hello @x-ma, 

Please review the following commits I made in branch 'dpup-version'.

0a08fe0256cb7e604b4c8adc1c3b8ac209257f36 (2014-02-04 16:22:15 -0800)
Bump package to 0.3.1 so we can use the MultiplexingCache

R=@x-ma