add usage and dependency info to readme

Author: toddtreece

README.md

@@ -1,7 +1,93 @@
 # Adafruit IO Arduino Library [![Build Status](https://travis-ci.org/adafruit/Adafruit_IO_Arduino.svg?branch=master)](https://travis-ci.org/adafruit/Adafruit_IO_Arduino)
 
+This library provides a simple device independent interface for interacting with [Adafruit IO](https://io.adafruit.com) using Arduino.
+It allows you to switch beween WiFi (ESP8266, M0 WINC1500, & WICED), Cellular (32u4 FONA), and Ethernet (Ethernet FeatherWing)
+with only a two line change in your sketch.
+
+## Dependencies
+
+This library requires the latest version of the [Arduino IDE](https://www.arduino.cc/en/Main/Software) (tested with v1.6.10).
+
+### Adafruit Feather HUZZAH ESP8266 & Adafruit HUZZAH ESP8266 Breakout
+
+* Latest version of the [ESP8266 Arduino Core](https://github.com/esp8266/Arduino#installing-with-boards-manager)
+* Latest version of the [Adafruit MQTT Library](https://github.com/adafruit/Adafruit_MQTT_Library)
+
+### Adafruit Feather M0 WiFi with ATWINC1500
+
+* Latest version of the [Arduino SAMD Arduino Core](https://github.com/arduino/ArduinoCore-samd)
+* Latest version of the [Adafruit SAMD Arduino Core](https://github.com/adafruit/ArduinoCore-samd)
+* Latest version of the [Adafruit MQTT Library](https://github.com/adafruit/Adafruit_MQTT_Library)
+
+### Adafruit WICED Feather WiFi
+
+* Latest version of the [Adafruit WICED Arduino Core](https://github.com/adafruit/Adafruit_WICED_Arduino)
+* Latest version of the [Adafruit MQTT Library](https://github.com/adafruit/Adafruit_MQTT_Library)
+
+### Adafruit Feather 32u4 FONA
+
+* Latest version of the [Adafruit AVR Arduino Core](https://github.com/adafruit/Adafruit_Arduino_Boards)
+* Latest version of the [Adafruit MQTT Library](https://github.com/adafruit/Adafruit_MQTT_Library)
+* Latest version of the [Adafruit FONA Library](https://github.com/adafruit/Adafruit_FONA)
+
+### Adafruit Ethernet FeatherWing
+
+The Ethernet FeatherWing will also require a 32u4, M0, or ESP8266 based Feather. Any Arduino cores
+required by the host Feather board will also be required.
+
+* Latest version of the [Adafruit Ethernet2 Library](https://github.com/adafruit/Ethernet2)
+* Latest version of the [Adafruit MQTT Library](https://github.com/adafruit/Adafruit_MQTT_Library)
+
+## Usage
+
+The included examples sketches will walk you through all of the features of the library.
+They can be used on all platforms, but they default to WiFi. To change between platforms,
+you will need to change two lines of code in the example. It is recommended that you start with
+one of the Adafruit WiFi feathers before moving on to Cellular or Ethernet.
+
+The examples below demonstrate how to switch between platforms.
+
+### WiFi (ESP8266, M0 WINC1500, WICED)
+
+```ino
+#include "AdafruitIO_WiFi.h"
+AdafruitIO_WiFi io(IO_USERNAME, IO_KEY, "your_wifi_ssid", "your_wifi_pass");
+```
+
+### Cellular (32u4 FONA)
+
+```ino
+#include "AdafruitIO_FONA.h"
+AdafruitIO_FONA io(IO_USERNAME, IO_KEY);
+```
+
+If you need to set APN info, you can do so by adding a call to `io.setAPN()` after `io.connect()` in the `setup()` function.
+
+```ino
+void setup() {
+
+  // start the serial connection
+  Serial.begin(115200);
+
+  // connect to io.adafruit.com
+  io.connect();
+
+  io.setAPN(F("your_apn"), F("your_apn_user"), F("your_apn_pass"));
+
+}
+```
+
+### Ethernet (Ethernet FeatherWing)
+
+```ino
+#include "AdafruitIO_Ethernet.h"
+AdafruitIO_Ethernet io(IO_USERNAME, IO_KEY);
+```
+
 ## Compatibility
 
+Last test with `v2.0.0` on 08/10/2016.
+
 Example            | ESP8266      | M0 WINC1500  | WICED       | FONA 32u4   | Ethernet*  |
 ------------------ | :----------: | :----------: | :---------: | :---------: | :--------: |
 00_publish         |      ✓       |      ✓       |      ✓      |      ✓      |      ✓     |
@@ -11,7 +97,7 @@ Example            | ESP8266      | M0 WINC1500  | WICED       | FONA 32u4   | E
 04_location        |      ✓       |      ✓       |      ✓      |      ✓      |      ✓     |
 05_type_conversion |      ✓       |      ✓       |      ✓      |      ✓      |      ✓     |
 
- * Feather ethernet wing tested with Feather M0 Proto
+* * Feather ethernet wing tested with Feather M0 Proto*
 
 ## License
 Copyright (c) 2016 [Adafruit Industries](https://adafruit.com). Licensed under the [MIT license](/LICENSE?raw=true).