Support post-1.0.0-rcXX releases of Nuxt

[LoneRifle]

There have now been 4 minor releases of Nuxt post-1.0, but these now require at least Node 8 to use. Transpilation of Nuxt itself would now be necessary to support Node 6, in use by both AWS Lambda and Google Cloud Functions.

I hence propose that the build process is changed to include a phase to transpile Nuxt to Node 6-compatible code. The GCF handler at prod/server should also be modified with the necessary shims to support needed Node 8 features. Prior work has been done with phlogisticfugu/perfect-paca, so this can serve as the basis of doing the same thing with this codebase.

[AndreReif]

Please write a step by step introduction for the implementation of additional Npms (like vuetify). At which points the implementation must be deposited.

The implication of ("@ nuxtjs / onesignal", "@ nuxtjs / pwa") was not a problem.