4.0.0

[IMPROVEMENT] Add .open for short-lived reporting that does not leave sockets around #96 by @grosser
[IMPROVEMENT] Extract batch logic into a class #95 by @grosser
[IMPROVEMENT] Extract connection for separation of concerns #94 by @grosser
[IMPROVEMENT] Fail fast on unknown options #93 by @grosser
[IMPROVEMENT] Always lazy connect #92 by @grosser
[IMPROVEMENT] Batch events and service checks too #88 by @grosser
[IMPROVEMENT] Remove bad argument after options #83 by @grosser
[IMPROVEMENT] Reduce object allocation and make all strings frozen on ruby 2.3+ #78 by @grosser

Breaking changes

Remove deprecated version method #91 by @grosser
port / host / tags / namespace can no longer be set on the instance to allow thread-safety #87 by @grosser
port / host / socket_path readers are now on statsd.connection
Make logger an instance var #90 by @grosser
Make format_service_check private #89 by @grosser
Improve code coverage / make format_event private #84 by @grosser
Set buffer size in bytes #86 by @grosser
max_buffer_size initializer argument removed and replaced with max_buffer_bytes (defaults to 8192)
max_buffer_size/max_buffer_size= methods removed