Relax the node version.
Relax the node version.

This change is needed in order to install zombie on node 5.x with
strict engine:

`npm config set engine-strict true`

aslakhellesoy/zombie,aslakhellesoy/zombie,jagoda/zombie,aslakhellesoy/zombie,assaf/zombie,mdlavin/zombie,jagoda/zombie,jagoda/zombie,mdlavin/zombie,assaf/zombie