Bump version to 0.4.1

Hello @chaosgame, @nicks, @giannic, 

Please review the following commits I made in branch 'xiao-0.4.1'.

a6ab136013e5d4c53990da2cc03797257adb0d37 (2014-09-08 14:47:38 -0700)
Bump version to 0.4.1

R=@chaosgame
R=@nicks
R=@giannic