Fix js builds and add testing (#1291)

* run emscripten tests on travis docker run, which has emcc. this verifies that the built wasm.js&binaryen.js works

* run binaryen.js and wasm.js tests before *and* after, to check the new build and also the bundled build

* updated js builds

Author: kripken

.travis.yml

@@ -72,7 +72,9 @@ jobs:
       before_install:
       - docker run -dit --name emscripten -v $(pwd):/src trzeci/emscripten:sdk-incoming-64bit bash
       script:
-      - docker exec -it emscripten bash ./build-js.sh -g && python -c "import check ; check.run_binaryen_js_tests()"
+      # run binaryen.js and wasm.js tests before and after building, so we see if the bundled
+      # version is good too
+      - docker exec -it emscripten bash ./travis-emcc-tests.sh
 
     # Build with gcc 6.3 and run tests on Alpine Linux (inside chroot).
     # Note: Alpine uses musl libc.