Tidy up Installation instructions

Now they look prettier on hexdocs

README.md

@@ -37,25 +37,24 @@ end
 
 ## Installation
 
-1. Add the package to your Mixfile:
+**Add the package to your Mixfile**
-   ```elixir
+
-   defp deps do
+```elixir
-     [{:isn, "~> 0.1"}]
+defp deps do
-   end
+  [{:isn, "~> 1.0"}]
-   ```
+end
+```
+
+**Add the isn extension to your database**
 
-2. Add the isn extension to your database
-   ```
     mix do isn.gen.migration, ecto.migrate
-   ```
 
-3. Register the postgrex extension in your Repo config
+**Register the postgrex extension in your Repo config**
-    ```elixir
+```elixir
-    config :books, MyApp.Repo,
+config :books, MyApp.Repo,
   adapter: Ecto.Adapters.Postgres,
   extensions: [{ISN, []}]
-
+```
-    ```
 
 ## Defined types