Update documentation for IO::Socket.

* Get rid of the POD errors as well as the useless `NOTE NOTE NOTE`
  lines that were littered throughout.
* Provide documentation and useful examples for each and every
  single constructor argument.
* Provide documentation for all methods made available.
* Where it makes sense, provide links to other documents that
  explain what the module is doing.

Previously, this relied heavily on the user knowing what they were
doing, rendering the documentation mostly pointless.

While this is not yet perfect, it's better than what we had before
and should be of help to developers of all skill levels.