Return undecoded content

[stefanodallapalma]

Closes #224

Return undecoded content by default via properties content and content_before.

Properties source_code and source_code_before are kept for back-compatibility only.
Note: these properties are the decoded content and content_before, respectively, and are not None if the file is of a supported language.

[ishepard]

Seemse like there are issues with mypy @stefanodallapalma 😄

[ishepard]

LGTM! Left minor comments.
Not sure whether we need to keep that warning on source_code.
Deprecated means we are gonna remove it soon, but we will not 😄 so not sure.
But that's another story, not on your PR

[stefanodallapalma]

@ishepard suggestions about fixing the issues on mypy? It seems to be related to a recent release of mypy; shall we downgrade it to a previous version, slightly change the test case, or (I'd prefer) silencing that error just for that line?

[codecov]

Codecov Report

Merging #231 (9390ec3) into master (02161a5) will decrease coverage by 0.28%.
The diff coverage is 83.33%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #231      +/-   ##
==========================================
- Coverage   98.36%   98.07%   -0.29%     
==========================================
  Files          15       14       -1     
  Lines        1039     1040       +1     
==========================================
- Hits         1022     1020       -2     
- Misses         17       20       +3     

Impacted Files	Coverage Δ
pydriller/domain/commit.py	97.91% <83.33%> (-0.77%)	⬇️
pydriller/__init__.py