Add bulk messaging capability

[PizzaBrandon]

Would you take a PR for adding bulk messaging support?

I recommend adding two options threshold and maxDelay like I used in good-tcp which follows the pattern established by the official good plugins, such as good-udp. These would inform the plugin if/how to buffer the messages before sending.

• threshold indicates how many messages to buffer before sending
• maxDelay tells the plugin the longest time it should hold a buffer before sending on next message (useful for programs with lower log frequency).

To maintain backward compatibility with existing plugin installations and make bulk transmission an opt-in feature, threshold would be set to 0.

[PizzaBrandon]

Commit with code based on initial recommendation: https://github.com/PizzaBrandon/good-loggly/commit/dce400db7845617330f5e62c3e711a5bba96417d

[arb]

Sure, we'd take a PR for that feature.