Run JVM/JS test sequentially on appveyor.
Run JVM/JS test sequentially on appveyor.

Previously, they ran in parallel causing OOM errors in Node.js

MasseGuillaume/scalameta,scalameta/scalameta,scalameta/scalameta,olafurpg/scalameta,MasseGuillaume/scalameta,scalameta/scalameta,DavidDudson/scalameta,MasseGuillaume/scalameta,scalameta/scalameta,DavidDudson/scalameta,olafurpg/scalameta,xeno-by/scalameta,xeno-by/scalameta,olafurpg/scalameta,xeno-by/scalameta,scalameta/scalameta