Provide a "Performance Tuning" documentation section

**Issue by [jrudolph](https://github.com/jrudolph)**
_Tuesday Feb 10, 2015 at 14:44 GMT_
_Originally opened as https://github.com/akka/akka/issues/16817_

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There are lots of knobs to turn to configure a common environment for high-performance networking e.g. on a Linux server. The spray community already collected lots of advice about how to do this. It could make sense to collect all of this information into a guide to get around the most common misconfigurations.

See the list of topics @RichardBradley already collected in spray/spray#917.

/cc @sirthias

Start with the topics collected in spray/spray#917, then inspect the repository's existing documentation structure to find the appropriate guide location. Organize guidance around common high-performance Linux networking misconfigurations and confirm that the resulting section covers the collected advice clearly.

Written by the indexing model from the issue text.