Merge pull request #1 from mattn/master

catch up to upstream mattn/go-xmpp
add STARTTLS support to TCP connections

- Add InsecureAllowUnencryptedAuth to options; go-xmpp will not leak
authentication in plaintext over TCP connections (breaks compatibility
with previous versions, slightly.)
fails.
- Add StartTLS to options; go-xmpp will use STARTTLS if the server
requires it or the user requests it.
- Add IsEncrypted method so sensitive clients can check if the
connection is TLS encrypted.
Merge pull request #36 from swdunlop/master

add STARTTLS support to go-xmpp
Only check the certificate's host name if InsecureSkipVerify is not set.
Merge pull request #37 from mgottschlag/skip-verify-hostname

Only check the certificate's host name if InsecureSkipVerify is not set.
fix DefaultConfig.ServerName not set when func NewClient(host...) is used
Merge pull request #40 from soygul/patch-1

fix DefaultConfig.ServerName not set when func NewClient(host...) is used
add send/sendorg return values
Merge pull request #41 from soygul/master

Add send/sendorg return values
Nickname can be specified when joining MUC

Client.JoinMUC now accept second argument as nickname.