_set_item() doesn't support integer values

[siddacious]

Currently when calling _set_item with an integer value such as one out of FancyLED's color.pack(), or even the example given in the docstring of _set_item, 0xFFFFFF.

Example/repro code:

import adafruit_dotstar
import board

led = adafruit_dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1)
led[0] = 0xFFFFFF

Traceback (most recent call last):
  File "code.py", line 5, in <module>
  File "adafruit_dotstar.py", line 190, in __setitem__
  File "adafruit_dotstar.py", line 160, in _set_item
TypeError: object of type 'int' has no len()

The issue is that the line in question is assuming that value is a tuple when it can be an int, as mentioned in the docstring. I have a fix I can submit as a PR; basically the function will already convert value to a tuple as rgb, we just need to check the length of rgb instead of value.

The same issue is there in the NeoPixel library though I haven't tested it yet. I can create an issue and PR there as well if this one is accepted.

[caternuson]

Fixed by #28