Update readme and added changelog

CHANGELOG

+
+SAMD CORE 1.6.1 2015.07.21
+
+* Added missing ATN pin definition
+* Added missing bootloader key/value pair in boards.txt (this allows to burn bootloader with Sam-ICE too)
+* Fixed min/max functions
+* Fixed hooks for Cortex-M RTOS
+* Fixed acknowledge of UART errors
+* Enabled C11/C++11
+* Fixed initialization in USB Device
+
+SAMD CORE 1.6.0  2015.06.15
+
+* First public release.
+

README.md

@@ -5,29 +5,10 @@ for Atmel's SAMD21 processor (used on the Arduino Zero board).
 
 ## Installation on Arduino IDE
 
+This core is available as a package in the Arduino IDE cores manager.
 Just open the "Boards Manager" and install the package called:
 
-```
-Arduino SAMD Boards (32-bit ARM Cortex-M0+)
-```
-
-## Hourly builds
-
-This repository is under a CI system that every hour checks if there are updates and
-builds a release for testing (the so called "Hourly builds").
-
-The hourly builds are available through Boards Manager. If you want to install them:
-  1. Open the **Preferences** of the Arduino IDE.
-  2. Add this URL `http://downloads.arduino.cc/Hourly/samd/package_samd-hourly-build_index.json` in the **Additional Boards Manager URLs** field, and click OK.
-  3. Open the **Boards Manager** (menu Tools->Board->Board Manager...)
-  4. Install **Arduino SAMD core - Hourly build**
-  5. Select one of the boards under **SAMD Hourly build XX** in Tools->Board menu
-  6. Compile/Upload as usual
-
-If you already installed an hourly build and you want to update it with the latest:
-  1. Open the **Boards Manager** (menu Tools->Board->Board Manager...)
-  2. Remove **Arduino SAMD core - Hourly build**
-  3. Install again **Arduino SAMD core - Hourly build**, the Board Manager will download the latest build replacing the old one.
+"Arduino SAMD Boards (32-bit ARM Cortex-M0+)"
 
 ## Support
 
@@ -49,6 +30,24 @@ to avoid duplicates.
 Contributions are always welcome. The preferred way to receive code cotribution is by submitting a 
 Pull Request on github.
 
+## Hourly builds
+
+This repository is under a Continuos Integration system that every hour checks if there are updates and
+builds a release for testing (the so called "Hourly builds").
+
+The hourly builds are available through Boards Manager. If you want to install them:
+  1. Open the **Preferences** of the Arduino IDE.
+  2. Add this URL `http://downloads.arduino.cc/Hourly/samd/package_samd-hourly-build_index.json` in the **Additional Boards Manager URLs** field, and click OK.
+  3. Open the **Boards Manager** (menu Tools->Board->Board Manager...)
+  4. Install **Arduino SAMD core - Hourly build**
+  5. Select one of the boards under **SAMD Hourly build XX** in Tools->Board menu
+  6. Compile/Upload as usual
+
+If you already installed an hourly build and you want to update it with the latest:
+  1. Open the **Boards Manager** (menu Tools->Board->Board Manager...)
+  2. Remove **Arduino SAMD core - Hourly build**
+  3. Install again **Arduino SAMD core - Hourly build**, the Board Manager will download the latest build replacing the old one.
+
 ## License and credits
 
 This core has been developed by Arduino LLC in collaboration with Atmel.