Disable nyan cat test reporter for CI

[SpaceK33z]

As much as I like the nyan cat reporter, it is a living hell when you need to quickly find out which test broke in the CI.

See e.g. this build failure at Travis. It contains 4370 lines of nyan cat particles my poor browser has to scroll through 🎱 .

So I'd suggest to either disable it for CI, or fully remove it.

[bebraw]

It could be conditional on Travis. So you get the default there (separate npm script).

[sokra]

I vote for full remove...

[bebraw]

Ok, PR welcome.