Datadog

**ThreadStats: metric type change**

`ThreadStats` count metrics (produced from the `increment`/`decrement` and `histogram` methods) are now reported with the `count`/`rate` metric type, instead of `gauge`.
As a result, for the corresponding metrics:
1. Metric queries can use the `.as_count()`/ `.as_rate()` functions to switch between count and rate representations.
2. The default time aggregation uses a sum instead of an average. **This may affect the representation of existing metric queries, thus, monitors' definitions and metric graphs.**

See [242][] (thanks [nilabhsagar][]) for more details.


* [BUGFIX] ThreadStats: Send count metrics with `Rate` metric type, [242][] (thanks [nilabhsagar][])
* [IMPROVEMENT] ThreadStats: Flush all metrics on exit, [221][]

* [BUGFIX] Dogshell: Service checks can be sent with optional parameters set to null values, [241][] (thanks [timvisher][])
* [BUGFIX] Dogwrap: Respect the output channel encoding format, [236][] (thanks [martin308][])
* [FEATURE] DogstatsD: Add beta support for sending global distribution metrics, [249][]

* [BUGFIX] API: Discard non-null parameters in `api.ServiceCheck.check`method, [206][], [207][] (thanks [ronindesign][])
* [BUGFIX] API: Update HTTP method from `GET` to `POST` for `api.Screenboard.share` method, [234][] (thanks [seiro-ogasawara][])
* [BUGFIX] Dogwrap: Encode from unicode before writing to stdout, stderr, [201][], [203][] (thanks [ronindesign][])
* [FEATURE] API: Add `list` method to `Metric` resource, [230][] (thanks [jbain][])
* [FEATURE] DogStatsD: Add `socket_path` option to enable Unix socket traffic to DogStatsD 6, [199][]
* [IMPROVEMENT] DogStatsD: Improve performances, speed up payload construction, [233][] (thanks [shargan][])

* [FEATURE] Dogshell: Add filtering options to the `monitor show_all` command, [194][]

* [FEATURE] API: Add metric metadata endpoints [181][]
* [IMPROVEMENT] API: Disable redirection following with `urlfetch` HTTP library [168][] (thanks [evanj][])
* [IMPROVEMENT] API: Increase default timeout from 3 to 60 seconds [174][] (thanks [ojongerius][])
* [IMPROVEMENT] DogStatsD: Better exceptions on system default route resolution failures [166][], [156][]
* [IMPROVEMENT] DogStatsD: Close sockets when freed [167][] (thanks [thehesiod][])

**Logging**

`dd.datadogpy` logger name is no longer. `datadog` now uses logger names matching the project hierarchy, i.e.
* `datadog.api`
* `datadog.statsd`
* `datadog.threadstats`

By default, `datadog` loggers are set with a do-nothing handler ([`NullHandler`](https://docs.python.org/3/howto/logging.html#configuring-logging-for-a-library)).

To setup a different handler, one can add a handler
python
import logging

logging.getLogger("datadog").addHandler(...)


Changes
* [FEATURE] DogStatsD: Provide elapsed time from the `timed` decorator, [154][] (thanks [tuukkamustonen][])
* [FEATURE] DogStatsD: Allow starting and stopping `timed` manually, [155][] (thanks [tuukkamustonen][])
* [IMPROVEMENT] DogStatsD: Support timing for coroutine functions on Python 3.5 or higher, [146][] (thanks [thehesiod][])
* [OTHER] Rename loggers and set null handlers, [161][]