there is no need to make a difference between DATA SENT and STANZA SENT
all data that is sent is also always only a single stanza

Fixes #53

We only had a data received/sent event which was enough for a long time
because servers used one tcp packet per stanza.

Now servers send multiple stanzas in one tcp packet, data received/sent
can contain more than one stanza which makes this new event necessary

https://tools.ietf.org/html/rfc6331

RC4-SHA is insecure and TLS1.2 should be on almost all xmpp servers

Fixes #52

with HTTP Transports like BOSH we dont need ALPN, so it should always
be False

Fixes #51

Some servers add à `optional` tag to inform us that no session is needed

Correct handling of Socks5 server replies (gajim/#8914)

See merge request !15

Fix UnicodeDecodeError exceptions when connecting with Socks5 proxy

Closes #48

See merge request !14

send unrequested ack when we haven't acked more than 100 stanza

Closes #45 and gajim#8758

See merge request !10

Cleanups, fix for logic error in code that checks for invalid file handles

See merge request !13