Use loggly bulk API

[Vincent--]

See https://www.loggly.com/docs/http-bulk-endpoint/

With the bulk API and some tweaking on the number of output workers and the flush size, the speed increased by around 50 times on my setup.

[Vincent--]

Next steps is to implement the multi_receive(events) to support logstash 2.2.x
See https://www.elastic.co/blog/logstash-2-2-0-and-2-1-2-released
and https://www.elastic.co/guide/en/logstash/current/_how_to_write_a_logstash_output_plugin.html

[torrancew]

+1 here, this is a huge design flaw with the current plugin. Connections are set up/torn down for each event in the current model. HTTPS and Proxies only exacerbate this.

[suyograo]

@Vincent-- apologies for not moving on this PR. Can you please rebase? I can merge this then

[Vincent--]

@suyograo, done 👍

[bangonkali]

Are there any plans to merge this?

[joshuabaird]

Is this ever going to be merged? This plugin is not usable for production in it's current state.

[webmat]

Sorry for the delay in getting to this, especially to @Vincent-- , who's been responsive in everything the team asked. This plugin doesn't have an active maintainer (see #20), so it's hard for us to dedicate much time to it.

I'll try to get this merged shortly.

[webmat]

This has been merged and expanded upon. Published as v4.0.0.

[webmat]

Very late, but thanks @Vincent-- for your contribution!