Update Readme

Author: webdeb

README.md

@@ -1,10 +1,14 @@
 # Thumbox
 
+Generate secure [thumbor](http://thumbor.org) urls on the fly.
+
 [![Build Status](https://travis-ci.org/webdeb/thumbox.svg?branch=master)](https://travis-ci.org/webdeb/thumbox)
 
+#### The signature generation is tested against the original thumbor implemention.
+
 ## Installation
 
-[available in Hex](https://hex.pm/thumbox), the package can be installed
+[available in Hex](https://hex.pm/packages/thumbox), the package can be installed
 by adding `thumbox` to your list of dependencies in `mix.exs`:
 
 ```elixir
@@ -15,6 +19,33 @@ def deps do
 end
 ```
 
-Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
-and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
-be found at [https://hexdocs.pm/thumbox](https://hexdocs.pm/thumbox).
+## Config
+
+```elixir
+config :thumbox,
+  server: "https://thumbor.example.com", # The thumbor server
+  origin: "my-app.com", # The hostname of the original images
+  secret: "s3cr3t", # The shared secret key
+  types: %{
+    # Define your image types
+    profile_avatar: "200x200/smart",
+    blog_header: "1024x360",
+  }
+```
+
+_Note_: The origin option can also be an internal hostname, like "app"
+
+## Usage
+
+### gen_url(type, path, opts \\ [])
+
+```elixir
+Thumbox.gen_url(:profile_avatar, "uploads/some-user-avatar.jpg")
+=> "https://thumbox.example.com/<hmac-signature>/200x200/smart/my-app.com/uploads/some-user-avatar.jpg"
+```
+
+opts: You can also pass any option from the config to the url generation on the fly.
+
+## License
+
+MIT