Fix CHANGELOG layout

CHANGELOG

@@ -4,7 +4,7 @@ For a more detailed treatment of changes, please see the commit history of the g
 
 Version 2.1.0 (18/10/18 joe@comp.lancs.ac.uk)
    - Refactor of motion sensor devices to support a range of accelerometer/magnetometer 
-	 sensors through abstract high level classes and concrete device specific subclasses.
+     sensors through abstract high level classes and concrete device specific subclasses.
    - Introduction of resusable 3D coordinate space transformation code.
    - Autodetection algorithm for I2C based accelerometer/magnetometer sensors.
    - Add support for LSM303 accelerometer/magnetometer sensor.
@@ -17,19 +17,18 @@ Version 2.1.0 (18/10/18 joe@comp.lancs.ac.uk)
      local magnetic fileds, such as those caused by a battery pack.
    - Updates to heap memory allocator. The MicroBitHeapAllocator now replaces
      the GNU libc heap allocator, rather than exisitng in parallel with it, in
-	 order to reduce memory fragmentation and ensure that all allocations
-	 benefit from multiple heap region support and interrupt safety.
+     order to reduce memory fragmentation and ensure that all allocations
+     benefit from multiple heap region support and interrupt safety.
    - Added new bluetooth partial flashing service, that allows rapid
-  	 reprogramming of the micro:bit over bluetooth in the common case.
+     reprogramming of the micro:bit over bluetooth in the common case.
    - Improved graphics for bluetooth pairing mode.
    - Support to allow explicit launch of conmpass calibration algorithm via BLE characteristic.
    - Support for integrated hardware quadrature decoder
 
    - Minor bug fixes/code optimisations including:
        - the message bus event routing code to support multiple event listeners 
-	     with the same id, value and context.
-	   - accelerometer pitch measurement algorithm now has a full 0..360 degree 
-	     range.
+         with the same id, value and context.
+	   - accelerometer pitch measurement algorithm now has a full 0..360 degree range.
 	   - Support for SHAKE gesture recognition in tight loops.
 	   - prevent device lockups when routing UART pins to the edge connector.
 	   - support for changing RADIO frequency whilst active.