Tesseract C API
As suggested by zdenop on https://github.com/tesseract-ocr/tesseract/issues/85#issuecomment-139132765 , using the C API could have many advantages:
- faster
- no annoying fork() + exec()
- no temporary file
- could avoid annoying regression like https://github.com/jflesch/paperwork/issues/392
To check: thread safety.
https://github.com/tesseract-ocr/tesseract/wiki/APIExample#c-api-in-python