[vz-dev] [volkszaehler/vzlogger] 51f5dd: Change travis to bionic (#412)

[Matthias Behr]

  Branch: refs/heads/master
  Home:   https://github.com/volkszaehler/vzlogger
  Commit: 51f5dd3b29fa5fa972279759b0c3569b10381d62
      https://github.com/volkszaehler/vzlogger/commit/51f5dd3b29fa5fa972279759b0c3569b10381d62
  Author: Matthias Behr <mbehr at mcbehr.de>
  Date:   2020-01-13 (Mon, 13 Jan 2020)

  Changed paths:
    M .travis.yml
    M src/vzlogger.cpp

  Log Message:
  -----------
  Change travis to bionic (#412)

* Fix travis build and do out of source build for vzlogger

* Use bionic for travis builds and gcc7/8.

Activated/fixed clang-format check.
Fixed one clang-format complain.
Updated leptonica to v1.79 (1.71 was removed)