Add coverage analysis, Coveralls about promise HOT 3 CLOSED

On BuckleScript, we need to be able to exclude the test suite.

1. With bs-platform > 6.0.3, it will be possible to pass --exclude-file to Bisect_ppx, which can exclude all test files in one swoop. This is not ideal, as --exclude-file is for working around build system issues.
2. The right way to fix this is to adjust the bsconfig.json schema to be able to specify ppx-flags per directory, so we can specify them in src/ only.
3. For now, we are using [@@@coverage exclude file] in each test file, which is annoying, but less annoying than installing bs-platform master as in (1).

from promise.

Development with BuckleScript or esy is now locked to OCaml 4.06 and BuckleScript 6.x.x, until aantron/bisect_ppx#220 is resolved.

from promise.

Blocked on better integration of Bisect_ppx with BuckleScript (rescript-lang/rescript-compiler#3761).

I disabled coverage on JS for now, because it's too annoying not to be able to use Bisect_ppx as a dev PPX. Coverage is still working on native, because the native library is not published to any package managers.

from promise.