WSGI Content-Length and Transfer-Encoding

[cirospaciari]

this is a WIP for #74

• Use chunked when Content-Length is absent
• Use Content-Length and try_end on happy path
• Close connection if Content-Length is too small
• add on_writable and on_aborted to send more chunks that failed to send with try_end

PS. This will require new binaries

[cirospaciari]

@ckcollab thanks to get the type, I think I just typed too fast at this moment lol I think today I will finish this PR