docs/esp8266/tutorial: Update since esptool 1.3 added Python 3 support.

esptool 1.3 now supports both Python 2.7 and 3.4+.
Updated github link to now-official espressif repo.

docs/esp8266/tutorial/intro.rst

@@ -72,15 +72,17 @@ For best results it is recommended to first erase the entire flash of your
 device before putting on new MicroPython firmware.
 
 Currently we only support esptool.py to copy across the firmware.  You can find
-this tool here: `<https://github.com/themadinventor/esptool/>`__, or install it
-using pip (at least version 1.2.1 is required)::
+this tool here: `<https://github.com/espressif/esptool/>`__, or install it
+using pip::
 
     pip install esptool
 
-It requires Python 2.7, so you may need to use ``pip2`` instead of ``pip`` in
-the command above.  Any other
-flashing program should work, so feel free to try them out, or refer to the
-documentation for your board to see its recommendations.
+Versions starting with 1.3 support both Python 2.7 and Python 3.4 (or newer).
+An older version (at least 1.2.1 is needed) works fine but will require Python
+2.7.
+
+Any other flashing program should work, so feel free to try them out or refer
+to the documentation for your board to see its recommendations.
 
 Using esptool.py you can erase the flash with the command::
 
@@ -88,7 +90,7 @@ Using esptool.py you can erase the flash with the command::
 
 And then deploy the new firmware using::
 
-    esptool.py --port /dev/ttyUSB0 --baud 460800 write_flash --flash_size=detect 0 esp8266-2016-05-03-v1.8.bin
+    esptool.py --port /dev/ttyUSB0 --baud 460800 write_flash --flash_size=detect 0 esp8266-20170108-v1.8.7.bin
 
 You might need to change the "port" setting to something else relevant for your
 PC.  You may also need to reduce the baudrate if you get errors when flashing
@@ -99,7 +101,7 @@ For some boards with a particular FlashROM configuration (e.g. some variants of
 a NodeMCU board) you may need to use the following command to deploy
 the firmware (note the ``-fm dio`` option)::
 
-    esptool.py --port /dev/ttyUSB0 --baud 460800 write_flash --flash_size=detect -fm dio 0 esp8266-2016-05-03-v1.8.bin
+    esptool.py --port /dev/ttyUSB0 --baud 460800 write_flash --flash_size=detect -fm dio 0 esp8266-20170108-v1.8.7.bin
 
 If the above commands run without error then MicroPython should be installed on
 your board!
@@ -158,7 +160,9 @@ after it, here are troubleshooting recommendations:
   esptool.py, which had a different programming algorithm::
     pip install esptool==1.0.1
   This version doesn't support ``--flash_size=detect`` option, so you will
-  need to specify FlashROM size explicitly (in megabits).
+  need to specify FlashROM size explicitly (in megabits). It also requires
+  Python 2.7, so you may need to use ``pip2`` instead of ``pip`` in the
+  command above.
 
 * The ``--flash_size`` option in the commands above is mandatory. Omitting
   it will lead to a corrupted firmware.
@@ -179,7 +183,7 @@ after it, here are troubleshooting recommendations:
   application in the ESP8266 community.
 
 * If you still experience problems with even flashing the firmware, please
-  refer to esptool.py project page, https://github.com/themadinventor/esptool
+  refer to esptool.py project page, https://github.com/espressif/esptool
   for additional documentation and bug tracker where you can report problems.
 
 * If you are able to flash firmware, but ``--verify`` option or