Add alphanumeric font and scrolling

Adds alphanumeric font and scrolling.

show('1234')
show('cool')
scroll('hello world')
scroll(list(tm1637._SEGMENTS))

Backwards compatibility issue:
If you are using tm1637._SEGMENTS, the blank and dash characters have been moved to the end of the font.

Previous font: 0-9, a-f, blank, dash
New font: 0-9, a-z, blank, dash, star

blank was segment 16 and is now segment 37.
dash was segment 17 and is now segment 38.

Brightness, temperature and pin toggling

v1.2.0

Add temperature, fix brightness, change how pins are toggled

MicroPython 1.9

v1.1.0

Github markdown syntax error

Initial

v1.0.0

Readme