HT1621 driver

[rm-hull]

Fixes #35

[thijstriemstra]

not sure why the (as purchased) part is in there.

My ordered display also arrived and I'll test this asap.

[rm-hull]

It looks like there are quite a few different variants that have 4, 5, 8 or 12 characters on the display. That statement was really just a disguised disclaimer saying it works on the 6 character device i suppose.

[thijstriemstra]

@rm-hull I'm trying to test this branch and started with:

$ python examples/demo.py --display ht1621
Traceback (most recent call last):
  File "examples/demo.py", line 99, in <module>
    main()
  File "examples/demo.py", line 54, in main
    device = get_device()
  File "/home/pi/projects/luma.examples/examples/demo_opts.py", line 51, in get_device
    device = cmdline.create_device(args)
  File "/home/pi/projects/luma.core/luma/core/cmdline.py", line 136, in create_device
    device = Device(spi, **vars(args))
TypeError: __init__() got multiple values for argument 'gpio'

Same with python examples/demo.py --display ht1621 --interface=spi..

[thijstriemstra]

Started adding some tests for issue in prev comment in term-bgcolor-79 of luma.core (rm-hull/luma.core#81).