Updates README.md with new slugger version

Author: sobolevn

README.md

@@ -15,7 +15,7 @@ Add `slugger` to your list of dependencies in `mix.exs`:
 ```elixir
 def deps do
   [
-    {:slugger, "~> 0.1.0"},
+    {:slugger, "~> 0.2"},
   ]
 end
 ```