crypto.createHash fix for node.js < 11

This PR will update the `sha1()` function @ [lib/protocol/Auth.js](https://github.com/felixge/node-mysql/blob/master/lib/protocol/Auth.js#L5) to update the `crypto.createHash` function to use the `.write()` & `.end()` functions vs. the depreciated `.update()` & `.digest()` methods when working with node.js < v0.10.*

I tried finding the exact version which removes the `.update()` & `.digest()` functions and through my tests I could only determine it to be between `v0.9.*` & `v0.10.*`.