Updated SHRY. Fixed the bug reported in the discussion #12

[kousuke-nakano]

I have fixed the bug reported in the discussion #12.

• Added atol to the np.isclose calls in core.py. The default value was atol=1e-8 -> atol=const.DEFAULT_ATOL or atol = self._atol.
• Introduced max_denominator=int(1 / const.DEFAULT_ATOL) argument to to_int_dict and inted_composition methods in the core.py module.
• SHRY prints comments about the choice of atol (i.e., precision) if one comes across an error related to this.
• Change the default --atol value in the script.py. default=const.DEFAULT_SYMPREC -> default=const.DEFAULT_ATOL. Is it a bug?
• Updated test_core.py triggered by pytest such that it uses the default values for SYMPREC, ANGLE_TOLERANCE, and ATOL.
• A GitHub action (shry-pytest.yml) is triggered also by a pull-request.
• Added a new meta-programing line for the Composition.formula property to use our tolerance (atol).