Update version to v2.0.0-pre.0

Author: fhunleth

mix.exs

@@ -1,7 +1,7 @@
 defmodule Circuits.I2C.MixProject do
   use Mix.Project
 
-  @version "1.2.2"
+  @version "2.0.0-pre.0"
   @description "Use I2C in Elixir"
   @source_url "https://github.com/elixir-circuits/circuits_i2c"