Update Tesseract for testing

Hello,

it would be great if we could add the next stable version of Tesseract for testing. In addition we could update the version of the operating system. I mean, why not 😌?

1. Tesseract (current 3.04.01) to 4.1.0 (ppa ~alex-p/+archive/ubuntu/tesseract-ocr, required)
2. Ubuntu Ubuntu Xenial 16.04 (current) to Bionic 18.04 (optional)

Reasons:

• Unit tests broke in a PR https://github.com/madmaze/pytesseract/pull/215, b/c of an old version of Tesseract and/or Leptonica
• Feature requests like https://github.com/madmaze/pytesseract/issues/172 (related to https://github.com/tesseract-ocr/tesseract/issues/785#issuecomment-451682596) require a newer version of Tesseract

Solution:

We could use Travis to test pytesseract with Tesseract-OCR 3.04.01 and 4.1.0 on Bionic 18.04 using a simple Dockerfile. I can do that and create a PR, but in this case it would be great to get some opinions first.

Edit:

Fix and change Xenial version from 14.04 to 16.04.

[int3l]

Yep, that’s fine by me.

[johnthagen]

@int3l I don’t have a strong preference, but I’d recommend we just use the stock beta version to keep the Travis configuration simpler.