Prefer documentation website for guides

"GettingStarted.md" is available as "Installation" at:
http://docs.appsignal.com/elixir/installation.html

"Phoenix.md" is available as "Integrating with Phoenix" at:
http://docs.appsignal.com/elixir/integrations/phoenix.html

Add basic details and links to resources in README

README.md

@@ -1,27 +1,61 @@
 # AppSignal agent for Elixir / Phoenix
 
-This library collects error and performance data from your Elixir
-applications and sends it to [AppSignal](https://appsignal.com).
-
 [![Build Status](https://travis-ci.org/appsignal/appsignal-elixir.png?branch=master)](https://travis-ci.org/appsignal/appsignal-elixir)
 [![Hex pm](http://img.shields.io/hexpm/v/appsignal.svg?style=flat)](https://hex.pm/packages/appsignal)
 
-**NOTE: This library is beta software, and still under development. API changes might still occur without notice. Please refer to the [Roadmap](Roadmap.md) document for more information.*
+AppSignal solves all your Elixir monitoring needs in a single tool. You and your
+team can focus on writing code and we'll provide the alerts if your app has any
+issues.
+
+**NOTE: This library is beta software, and still under development. API changes
+might still occur without notice. Please refer to the [Roadmap](Roadmap.md)
+document for more information.*
+
+- [AppSignal.com website](https://appsignal.com/)
+- [AppSignal for Elixir documentation](http://docs.appsignal.com/elixir/)
+- [Package documentation](https://hexdocs.pm/appsignal/)
+- [Support](support@appsignal.com)
+
+## Description
+
+The AppSignal for Elixir package collects exceptions and performance data from
+your Elixir applications and sends it to AppSignal for analysis. Get alerted
+when an error occurs or an endpoint is responding very slowly.
+
+## Installation
 
-See [Getting started](https://hexdocs.pm/appsignal/gettingstarted.html) on how to use this library.
+Please follow the [installation
+guide](http://docs.appsignal.com/elixir/installation.html) on how to install
+and use this library.
 
-Full documentation: https://hexdocs.pm/appsignal/
+If you're using the Phoenix framework, please also follow the [integration guide
+for Phoenix](http://docs.appsignal.com/elixir/integrations/phoenix.html).
 
+## Usage
 
-## Branches and versions
+AppSignal will automatically monitor requests, report any exceptions that are
+thrown and any performance issues that might have occurred.
+
+You can also add extra information to requests by adding custom
+instrumentation. Read more in our [instrumentation
+guide](http://docs.appsignal.com/elixir/instrumentation/).
+
+## Configuration
+
+A complete list of all configurable options for AppSignal for Elixr is
+available in [our
+documentation](http://docs.appsignal.com/elixir/configuration/).
+
+## Development
+
+### Branches and versions
 
 The `master` branch corresponds to the current release of the
 library. The `develop` branch is used for development of features that
 will end up in the next minor release. If you fix a bug open a pull
 request on `master`, if it's a new feature on `develop`.
 
-
 ## License
 
-The Appsignal library source code is released under the MIT
-License. Check the [LICENSE](LICENSE) file for more information.
+The AppSignal for Elixir package source code is released under the MIT License.
+Check the [LICENSE](LICENSE) file for more information.