Upgrade CI setup

[vemv]

Misc self-explanatory changes that go in the following direction:

• Expand CI matrix
  • more JDKs, more nrepl / cljs versions
• Make tests faily more informatively

Build is green in my account.

[vemv]

🍻!

Could you cut a release? Would be nice to use it in refactor-nrepl's suite (particularly for https://github.com/nrepl/piggieback/commit/b0740a7ccd6a1248560475da3747081068460987)

[bbatsov]

Yeah, I can do this later today.