chore(travis): disable iojs build until mockfs gets forked/fixed :(
chore(travis): disable iojs build until mockfs gets forked/fixed :(

Sorry guys .-. I'd really like to cover as much of the node ecosystem as
possible, and I guess mock-fs is making that a bit difficult for the
time being. 3.x seems to be a recent release, so maybe someone will
contribute a fix. Might even be me.

Closes #20

jcope2013/broccoli-persistent-filter,broccolijs/broccoli-filter,chadhietala/broccoli-persistent-filter,caitp/cauliflower-filter,rwjblue/broccoli-persistent-filter,stefanpenner/broccoli-persistent-filter,matthewjh/cauliflower-filter,csantero/broccoli-persistent-filter,joliss/broccoli-filter