JavaScript CI is broken
After latest commits, JavaScript runtime is broken, at least for CI purposes:

```
$ ./run-javascript 
kaitai_struct/tests/spec/javascript/test_default_endian_expr_exception.js:3
testHelperThrows('DefaultEndianExprException', 'src/endian_expr.bin', KaitaiUndecidedEndiannessError);
                                                                      ^

ReferenceError: KaitaiUndecidedEndiannessError is not defined
    at Object.<anonymous> (kaitai_struct/tests/spec/javascript/test_default_endian_expr_exception.js:3:71)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)
    at kaitai_struct/tests/node_modules/mocha/lib/mocha.js:222:27
    at Array.forEach (native)
    at Mocha.loadFiles (kaitai_struct/tests/node_modules/mocha/lib/mocha.js:219:14)
    at Mocha.run (kaitai_struct/tests/node_modules/mocha/lib/mocha.js:487:10)
    at Object.<anonymous> (kaitai_struct/tests/node_modules/mocha/bin/_mocha:458:18)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Function.Module.runMain (module.js:441:10)
    at startup (node.js:140:18)
    at node.js:1043:3
```