Add support for MUC

Signed-off-by: Emilien Kenler <hello@emilienkenler.com>
Merge arunoda/node-simple-xmpp

Signed-off-by: Emilien Kenler <hello@emilienkenler.com>
Use whitespace keepalives instead of presence stanzas

Sending <presence> stanzas too frequently may cause issues with servers rate limiting the user (see issue #15). This switches to using whitespace for keepalives instead. 

From XMPP specs:

   One common method for checking the TCP connection is to send a space
   character (U+0020) between XML stanzas, which is allowed for XML
   streams as described under Section 11.7; the sending of such a space
   character is properly called a "whitespace keepalive" (the term
   "whitespace ping" is often used, despite the fact that it is not a
   ping since no "pong" is possible).
Fix groupchat event related variable

The from child follow this pattern: <room_name>@conference.<host_name>/<user_nick>

Signed-off-by: Emilien Kenler <hello@emilienkenler.com>
Add some documentation

Signed-off-by: Emilien Kenler <hello@emilienkenler.com>
Add one groupchat example

Signed-off-by: Emilien Kenler <hello@emilienkenler.com>
Merge pull request #11 from MiLk/master

Add support for MUC
Merge pull request #17 from Daniel15/patch-1

Use whitespace keepalives instead of presence stanzas
Merge remote-tracking branch 'upstream/master'

Conflicts:
	lib/simple-xmpp.js