docs: Add 2 images for tutorials.

docs/tutorial/script.rst

@@ -10,7 +10,7 @@ Connecting your pyboard
 Connect your pyboard to your PC (Windows, Mac or Linux) with a micro USB cable.
 There is only one way that the cable will connect, so you can't get it wrong.
 
-<img src="/static/doc/pyboard-usb-micro.jpg" alt="pyboard with USB micro cable" style="width:200px; border:1px solid black; display:inline-block;"/>
+.. image:: img/pyboard_usb_micro.jpg
 
 When the pyboard is connected to your PC it will power on and enter the start up
 process (the boot process).  The green LED should light up for half a second or

docs/tutorial/servo.rst

@@ -8,7 +8,7 @@ These motors have 3 wires: ground, power and signal.  On the pyboard you
 can connect them in the bottom right corner, with the signal pin on the
 far right.  Pins X1, X2, X3 and X4 are the 4 dedicated servo signal pins.
 
-<img src="/static/doc/pyboard-servo.jpg" alt="pyboard with servo motors" style="width:250px; border:1px solid black; display:inline-block;"/>
+.. image:: img/pyboard_servo.jpg
 
 In this picture there are male-male double adaptors to connect the servos
 to the header pins on the pyboard.