TCP connections aren't reused across batches

[rohitpaulk]

When we make requests to multiple batches, we construct a Net::HTTP object again and again - which internally creates a new TCP connection for every HTTP request.

This can be improved by reusing the Net::HTTP object.

[rohitpaulk]

PR opened: #149.

Here's the test script I used:

require 'segment/analytics'

analytics = Segment::Analytics.new({write_key: 'testkey'})

small_message = {
  user_id: 'abcd',
  event: 'abcd'
}

1000.times { analytics.track(small_message) }
analytics.flush

Before: 30s

→ time bundle exec ruby test_script.rb
bundle exec ruby test_script.rb  0.59s user 0.17s system 2% cpu 29.142 total

After patch: 8s

→ time bundle exec ruby test_script.rb
bundle exec ruby test_script.rb  0.55s user 0.14s system 8% cpu 7.986 total

Real-life performance improvements won't be this high (I'm running this from my laptop in India), but definitely substantial.

[rohitpaulk]

This had to be reverted because of #167, re-opening.