Add a rebuild command

Many users are having problems to use ijavascript because:
* there are no `zeromq` binaries for their platform
* the version of node.js has changed after the installation of ijavascript

I'd like to add a command (`ijsrebuild`) that:
* installs and/or informs the user about the required dependencies to rebuild the `zeromq` binary
* rebuilds the `zeromq` binary
* reinstalls the kernel spec