Revert "Upgrade to SockJS 0.3.8."

This reverts commit 86b978b0f371b2ca32a395f6f4c24bd3317566ea.

The commit breaks some nuanced node stream issues
that manifest as `meteor test-packages` handing
on Firefox. We'll remember to un-revert this revert
once devel is fixed (with a new release of Node)