websocket support & demos

split _ldap.pyx into coro.asn1.ber and coro.ldap.query

use cython quadtree implementation

websocket.__init__(): record the handler (for passing user/config info down)
websocket.read_thread(): catch ClosedError

backdoor.print_result(): override to print the result specially (e.g., pprint)

typo fix in emulation. ignore attribute error for socket BD settings

include emulation code

init close_it

since h76 reads delimited data, use request.client.stream for both protocols (a good idea anyway)

HTTP_Upgrade: new exception

The previous content was confusing, outdated, and unhelpful.