Godeps: update dependency for go-msgio

Otherwise there is the following failure when running godep restore:

fatal: reference is not a tree: 281b085dc602c4f0377438e20331f45a91bcdf9c
godep: restore: exit status 128

License: MIT
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Merge pull request #464 from chriscool/update_go_msgio_in_godeps

Godeps: update dependency for go-msgio