nails 0.4.0

[Nailgun](http://martiansoftware.com/nailgun/protocol.html) client and server protocols and a `Nail` trait that consuming crates can implement to plug in the logic that they would like to keep warm in a nailgun server.
Documentation
Builds

nails's sandbox limits

All the builds on docs.rs are executed inside a sandbox with limited resources. The limits for this crate are the following:

Available RAM 6 GB
Maximum rustdoc execution time 15 minutes
Maximum size of a build log 100 kB
Network access blocked
Maximum number of build targets 10

If a build fails because it hit one of those limits please open an issue to get them increased.