Expose the #compile method from bpf lib.

This will allow us to validate BPF strings in the UI without needing root permissions to open a live device.

Verification:
- [ ] Ensure that `Pcap.create('lo').compile("port 112")` does not* raise an error
- [ ] Ensure that `Pcap.create('lo').compile("port 999999")` *does* raise an error