fixing ALS Integration time consts for #6

[siddacious]

This addresses the integration time const bugs discovered by @ssagat in issue #6

[siddacious]

here's some output before and after the change, iterating through the IT values:

Ambient light: 4398
Ambient light: 4377
Ambient light: 4385
(+++++++_+
Ambient light: 8758
Ambient light: 8780
Ambient light: 8776
(+++++++_+
Ambient light: 17530
Ambient light: 17486
Ambient light: 17577
(+++++++_+
Ambient light: 52608
Ambient light: 35114
Ambient light: 35114
(+++++++_+
Ambient light: 4380
Ambient light: 4383
Ambient light: 4388
(+++++++_+
Ambient light: 8811
Ambient light: 8772
Ambient light: 8747
(+++++++_+
*********************************


after:
Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
Ambient light: 1103
Ambient light: 1097
Ambient light: 1105
(+++++++_+
Ambient light: 2211
Ambient light: 2205
Ambient light: 2208
(+++++++_+
Ambient light: 4405
Ambient light: 4417
Ambient light: 4422
(+++++++_+
Ambient light: 8853
Ambient light: 8819
Ambient light: 8848
(+++++++_+
Ambient light: 17679
Ambient light: 17738
Ambient light: 17738
(+++++++_+
Ambient light: 53147
Ambient light: 53147
Ambient light: 35330
(+++++++_+
*********************************

I think there may still be an issue with the scaling because the light level shouldn't change as you change the integration time, but it's better now