Testing

All tests work - assuming default precision of .6 for 'f' 'F' float
specs - not sure if sensible

'g','G' seems to not behave sensibly with the format spec --> not coded
in tests and not parsing because no obvious way to determine edge cases
(seems to use default precision of 6 if E form of precision is too large
it uses that?):
'{0:<6.3g}'.format(1234)
'1.23e+03'
'{0:<6.3g}'.format(123)
'123   '