fix uitls and support not tensor in Y_dict

[senwu]

Description of the problems or issues

1. Support non-tensor in Y_dict in dataset.
2. Support list of nparray input in prob_to_pred.

Checklist

• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.
• [ ] I have updated the CHANGELOG.rst accordingly.

[codecov[bot]]

Codecov Report

Merging #83 (fb4ef67) into master (6556055) will decrease coverage by 0.11%. The diff coverage is 60.00%.

@@            Coverage Diff             @@
##           master      #83      +/-   ##
==========================================
- Coverage   87.93%   87.82%   -0.12%     
==========================================
  Files          38       38              
  Lines        1741     1741              
  Branches      374      374              
==========================================
- Hits         1531     1529       -2     
- Misses        111      112       +1     
- Partials       99      100       +1     

Flag	Coverage Δ
unittests	87.82% <60.00%> (-0.12%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/emmental/data.py	83.33% <ø> (-0.60%)	:arrow_down:
src/emmental/utils/utils.py	85.12% <60.00%> (-1.21%)	:arrow_down: