Add .travis.yml for testing the PRs at https://travis-ci.com/apache/velocity-engine

[martin-g]

Remove unused imports in OldPropertiesTestCase. It failed compiling on my local because I use JDK 15 by default.

[arkanovicz]

From seeing the output, the failing test looks like a test isolation leak between ugly1.vtl and ugly2.vtl : ugly2 defines the #foo macro to render bar, ugly1 output should never display bar.

Looking at the code, I don't understand for now where it can come from, since in the SpaceGlobbing test case, each test is using its own engine, output filename and context. Behaviors should be totally hermetic, even ran in parallel, so for now it's a mystery to me.

[martin-g]

I think I figured it out:
it seems on TravisCI File[] directoryListing = dir.listFiles(); returns first "ugly2.vtl" and then `ugly.vtl" and due to this the context for ugly1 is "dirty".
I've moved the initialization of VelocityEngine one level/method later and now everything is OK.

Please let me know if you want me to squash the commits!

[arkanovicz]

Oh, well done. Hadn't thought of that.
Yes, squash, please.

[martin-g]

Squashed and force-pushed!
TravisCI is happy!