Update mix.exs

Author: Relrin

mix.exs

@@ -1,13 +1,13 @@
 defmodule Spotter.MixProject do
   use Mix.Project
 
-  @version "0.5.0"
+  @version "0.5.1"
 
   def project do
     [
       app: :spotter,
       version: @version,
-      elixir: "~> 1.7",
+      elixir: "~> 1.9",
       start_permanent: Mix.env() == :prod,
       description: description(),
       package: package(),