Reach >95% test coverage

[matterhorn103]

Current status:

Name                                  Stmts   Miss  Cover
---------------------------------------------------------
quanstants/__init__.py                   19      0   100%
quanstants/abstract_quantity.py         133     15    89%
quanstants/abstract_unit.py              36      2    94%
quanstants/config.py                    141     52    63%
quanstants/constant.py                   57      2    96%
quanstants/constants/__init__.py         15      9    40%
quanstants/constants/codata2018.py       78      0   100%
quanstants/constants/fundamental.py       9      0   100%
quanstants/dimensions.py                 46     14    70%
quanstants/exceptions.py                 14      0   100%
quanstants/format.py                    110     21    81%
quanstants/log.py                       217     58    73%
quanstants/prefix.py                     60      7    88%
quanstants/prefixes/__init__.py           5      1    80%
quanstants/prefixes/binary.py             9      0   100%
quanstants/prefixes/metric.py            25      0   100%
quanstants/quantity.py                  273     70    74%
quanstants/rounding.py                   36     11    69%
quanstants/temperature.py               123     30    76%
quanstants/uncertainties.py              60     16    73%
quanstants/unicode.py                    79      5    94%
quanstants/unit.py                      313     78    75%
quanstants/units/__init__.py            118     51    57%
quanstants/units/atomic.py                5      0   100%
quanstants/units/base.py                 15      0   100%
quanstants/units/chemistry.py             6      0   100%
quanstants/units/common.py               20      0   100%
quanstants/units/computing.py             7      0   100%
quanstants/units/imperial.py             52      0   100%
quanstants/units/logarithmic.py           9      0   100%
quanstants/units/natural.py               5      0   100%
quanstants/units/planck.py                5      0   100%
quanstants/units/prefixed.py             50      0   100%
quanstants/units/si.py                   50      0   100%
quanstants/units/temperatures.py          8      0   100%
quanstants/units/us.py                   29      0   100%
tests/test_config.py                     10      0   100%
tests/test_constants.py                   2      0   100%
tests/test_general.py                   429      2    99%
tests/test_imports.py                    12      0   100%
tests/test_quantity.py                   51      0   100%
tests/test_temperature.py                58      0   100%
tests/test_uncertainties.py             181      0   100%
tests/test_unicode.py                   116      0   100%
tests/test_unitreg.py                     9      0   100%
tests/test_units.py                       4      0   100%
---------------------------------------------------------
TOTAL                                  3109    444    86%

[matterhorn103]

In particular, need to add thorough unit tests for:

• unit.py
• quantity.py
• constant.py
• log.py

as currently these are only being tested by the automated tests of the README.