Fastify 2.0 support

[karlos1337]

Can't build my app since Fastify 2 upgrade, fastify-plugin breaks with:

Error: fastify-plugin - expected '^1.0.0' fastify version, '2.0.0' is installed

On removing that check from fastify-plugin source (~ line 65) all works fine again, not a suggestion, for sure will exists a better fix than that 😅 , but seems that this check is the only problem.

[mcollina]

One of the plugins you are using requires fastify v1. If you look at the stacktrace you'll see which one.

[karlos1337]

You're right, related with fastify/fastify-cors#17 , sorry