Fix CI on travis and include Python 3.8-dev by bluebird75 · Pull Request #76

Fix CI on travis and include Python 3.8-dev by bluebird75 · Pull Request #76 · dropbox/pyannotate

- install mypy version lower than 0.620 to avoid an error
- Use matrix syntax
- Workaround for python 3.7 and 3.8 not compiling on Trusty
- Add python 3.8-dev as target

mentioned this pull request

Aug 26, 2018

…yannotate into fixes-for-travis-ci

# Conflicts:
#	.travis.yml