please nest under a namespace (eg:simpleweb) to avoid name clashes

[timotheecour]

symbols should be under a namespace, and includes should be under a toplevel directory, eg:

#include crypto.hpp => #include simpleweb/crypto.hpp

[eidheim]

There are two small classes and a namespace outside of the SimpleWeb namespace. I'll move these inside SimpleWeb as well after a minute version release. This is actually being worked on in Simple-Web-Server at the moment (https://github.com/eidheim/Simple-Web-Server/commit/ec63c4345ea9a21bd21bf5588d462901282f8d2e).

I kept the directory structure simple due to the number of files, but will reconsider this for the next major version release.