Should unicode_pm mode be default True?

[jagerber48]

The current behavior is

>>> from sciform import Formatter
>>> sform = Formatter()
>>> print(sform(123.456, 0.789))
123.456 +/- 0.789
>>> sform = Formatter(unicode_pm=True)
>>> print(sform(123.456, 0.789))
123.456 ± 0.789

Users must explicitly opt in to using unicode pm mode. Is unicode ubiquitous enough that unicode_pm=True should be default? Can/should we go even further and entirely eliminate the '+/-' format entirely and only support '±'?

[jagerber48]

I am going to forward with having '±' be the default and dropping the unicode_pm option. Including default support for '±' seems like a good feature for this package, and I think most, if not all, text renderers can display the '±' character. If there is user demand for the ability to get the old unicode_pm=False behavior then that can be be added back in as a feature.

See #78