attention, chatstates, eme, ping: Add a docstring on the structs.

src/attention.rs

@@ -12,6 +12,7 @@ use error::Error;
 
 use ns;
 
+/// Structure representing an `<attention xmlns='urn:xmpp:attention:0'/>` element.
 #[derive(Debug, Clone)]
 pub struct Attention;
 

src/chatstates.rs

@@ -12,12 +12,23 @@ use error::Error;
 
 use ns;
 
+/// Enum representing chatstate elements part of the
+/// `http://jabber.org/protocol/chatstates` namespace.
 #[derive(Debug, Clone)]
 pub enum ChatState {
+    /// `<active xmlns='http://jabber.org/protocol/chatstates'/>`
     Active,
+
+    /// `<composing xmlns='http://jabber.org/protocol/chatstates'/>`
     Composing,
+
+    /// `<gone xmlns='http://jabber.org/protocol/chatstates'/>`
     Gone,
+
+    /// `<inactive xmlns='http://jabber.org/protocol/chatstates'/>`
     Inactive,
+
+    /// `<paused xmlns='http://jabber.org/protocol/chatstates'/>`
     Paused,
 }
 

src/eme.rs

@@ -12,9 +12,14 @@ use error::Error;
 
 use ns;
 
+/// Structure representing an `<encryption xmlns='urn:xmpp:eme:0'/>` element.
 #[derive(Debug, Clone)]
 pub struct ExplicitMessageEncryption {
+    /// Namespace of the encryption scheme used.
     pub namespace: String,
+
+    /// User-friendly name for the encryption scheme, should be `None` for OTR,
+    /// legacy OpenPGP and OX.
     pub name: Option<String>,
 }
 

src/ping.rs

@@ -13,6 +13,7 @@ use error::Error;
 
 use ns;
 
+/// Structure representing a `<ping xmlns='urn:xmpp:ping'/>` element.
 #[derive(Debug, Clone)]
 pub struct Ping;