Added support for Bungeecord's proxy_protocol option

[itzg]

I have a request itzg/docker-mc-proxy#51 from a user of my bungeecord Docker image (and indirectly itzg/mc-monitor#6 ) to support Bungeecord's proxy_protocol option.

Since this new configuration of Pinger needed to be combined with context/timeout support I decided to introduce a functional options pattern to allow for backward/forward compatible options on the New function.

For example:

	options := []mcpinger.McPingerOption{}
	if c.Timeout > 0 {
		options = append(options, mcpinger.WithTimeout(c.Timeout))
	}
	if c.UseProxy {
		options = append(options, mcpinger.WithProxyProto(c.ProxyVersion))
	}
	pinger := mcpinger.New(c.Host, uint16(c.Port), options...)

[raqbit]

Looks good!

I've been working on rebasing mc-pinger on mcproto, which is an implementation of the Minecraft protocol in Go: #9. mcproto started as the protocol bits of mc-pinger, but slowly got out of sync with added (de-)serialization code generation, support for SRV records and some other features. With these changes I've also redone the mc-pinger API, to make it more like net.Dial et al (Breaking change, but as the API surface is small it should not be much of an issue).

With this PR in mind, I think adding options to each of the Ping-functions would be nice, especially with a WithProtoOption() option to pass options to the underlying mcproto library (add custom packets, add proxy support, configure logging etc.)

If you have the time, I'd appreciate it if you could take a look at the mcproto draft PR and give some feedback so I know if I'm heading into the right direction with this new mc-pinger API.

I could merge this PR right now, but then I'd expect to be breaking the API with those changes. Another option is to include proxy support in mcproto, and then adding the option to the new mc-pinger API.

What do you like best?

[itzg]

That sounds like a great strategy and I'll definitely look over that PR.

To address the user request I would prefer to merge this PR. After that I can take my time with the subsequent release to incorporate the mcproto related changes.

[raqbit]

I've released v0.2.0 just now, next release will probably be the one including the mcproto changes.

Thanks!