Update documentation

[aaaaalbert]

The existing documentation on Affix is out of date, and not all of the existing code is helpful to get started. The Seattle Wiki has a couple of old "shim" documentation that might or might not be relevant to the current state of Affix.

On a high level, https://seattle.poly.edu/wiki/WritingShims-RepyV2 goes in the right direction I think, i.e. showing how an application can be amended to include Affixes, and then building one's own Affix.

Find my suggestions on a reworked version over here,

https://seattle.poly.edu/wiki/GettingStartedWithAffix

[ffund]

Perhaps we could start with a tutorial describing how to send netcat traffic through Affix with the proxy. This seems like a prerequisite for any dev tutorials, anyways.