[FEATURE REQUEST] Allow for histogram percentiles with more than two digits

[gmalouf]

Noticed the following when dogstatsd started up:

2017-06-24 03:26:10 | WARNING | dd.dogstatsd | config(config.py:316) | Histogram percentiles are rounded to 2 digits: 0.999 rounded

It would be nice to be able to have '99.9' and/or '99.99' percentiles. I know it can be done in statsd, so seems reasonable to support setting those percentiles up via datadog.conf.

[ryan-ju]

I need this too. Currently, the datadog.conf file ignores percentiles like 0.999, 0.9999.

[jameynelson]

Currently looking for this feature also.

[cozos]

We need this feature

[stefanc-ai2]

We need this feature too.