Bump to version 1.4.0

Bump to version 1.3.1

Bump to version v1.3.0

Bump to version v1.2.2

Bump to version 1.2.1

Bump to version 1.1.1

Bumped mdutils version 1.1.0

Update CHANGELOG.md

Use github_changelog_generator

Update travis, build for python 3.7, 3.8 and pypy3

Merge branch 'develop'