Update/Fix documentation

[carllerche]

The state of Mio documentation has fallen behind. This is due to the API being in flux. This issue is to track the work that is needed to get the documentation to a good state. Documentation issues will be linked for reference.

• Document Poll
• Update tutorial to use Poll instead
• Fix automated doc building (Evented Trait Docs are Hidden #319, Duplicate entries in docs #329)
• Fix out of date docs (out of date comment in the example PingPong server #403, Update example #323)
• Document points of confusion (TCP server hangs #380, When is it safe to clear a timeout? #358)
• Document configuring sockets (mio 0.3.7 -> mio 0.5 (and master) latency regression #442, Setting socket options immediately after connecting may fail #446)
• Interest options (I can not set event_loop.register to EventSet::error() | EventSet::hup() #443)
• Upgrade (Doc to upgarde from 0.5 to 0.6 #509)

[chancez]

https://crates.fyi/crates/mio/0.5.1/ seems to be working as a subsitite to the current docs. It does seem to have the fix for #319 as I can view EventedFd in it.

[carllerche]

Closing due to inactivity.