feat(build): add windows and osx builds to Travis

[moorereason]

Fixes #223
Fixes #224

[moorereason]

It looks like most of the "advanced" stuff in the Makefile may be a problem for Travis windows builds. I stripped a lot of that out to get it to build.

[xcoulon]

It looks like most of the "advanced" stuff in the Makefile may be a problem for Travis windows builds. I stripped a lot of that out to get it to build.

Ok, I understand. Well, this makes the whole "build" much simpler, in the end, so it's even better :)
At this point, I believe we should add support for macos (osx), too.

Please remove the WIP prefix on the PR title once you feel it's good to merge.

[moorereason]

I rebased this PR to clean up the git log. I'll update the OP to match the extended scope since we're adding OSX, too.

[xcoulon]

thanks for this PR, @moorereason ! The Makefile and the .travis.yml config file are now much simpler and having all platforms build on a single place is nice ;)