travis: don't test node v0.6
travis: don't test node v0.6

Travis doesn't work with it anymore it seems.
Not sure what the issue is.

See: https://travis-ci.org/TooTallNate/node-weak/jobs/48549573

robcolburn/node-weak,KenanSulayman/node-weak,kkoopa/node-weak,TooTallNate/node-weak,KenanSulayman/node-weak,fastest963/node-weak,fastest963/node-weak,kkoopa/node-weak,EvolveLabs/electron-weak,kkoopa/node-weak,robcolburn/node-weak,TooTallNate/node-weak,robcolburn/node-weak,unbornchikken/node-weak,EvolveLabs/electron-weak,fastest963/node-weak,unbornchikken/node-weak,EvolveLabs/electron-weak,TooTallNate/node-weak,KenanSulayman/node-weak,unbornchikken/node-weak