extend the Travis CI Build Matrix

[pointbazaar]

Hello,

i noticed your repo has many issues but has not been maintained in a long time.

So i wanted to make a PR in the Hacktoberfest spirit.

If this gets merged, please add the "hacktoberfest-accepted" tag.

I would have extended the build matrix more for macOS but i never build on that, so i don't know what would be appropriate.

Cheers!

[pointbazaar]

seems to fail on arch: arm64 build