Rename ce to calibrated_explanations

[rudymatela]

Closes: #3

As this is needed for publication at PyPI, see issue #3.

I initially tried to name the package ce on PyPI, but that name is reserved by PyPI and I get an error message -- I think it is too short. So I guess it makes sense to go with a more descriptive name "calibrated explanations".

PEP 423 details the rules for packages published at PyPI. The main guideline is that the module name should match the package name. Following the guidelines there (which I won't repeat here for brevity), my suggestion is:

• calibrated_explanations as the module name
• calibrated-explanations as the package name

[rudymatela]

I merged this already not to delay this further.