Remove logging from digital pathology transforms (#297)

closes #114

Removes the try/except wrappers with logging of errors from the digital pathology transforms added in #100. 

Also renames a variable `to_cupy` to `to_numpy` instead to reflect its actual function.

**For reviewers**: There appear to be many lines changed here, but it is mostly a change in indentation due to removal of `try/except` blocks with `_logger` calls. Also some nested function definitions within `color_jitter` were moved outside of that function.

Authors:
   - Gregory Lee (https://github.com/grlee77)

Approvers:
   - Gigon Bae (https://github.com/gigony)
   - https://github.com/jakirkham