Merge pull request #19 from fibonacci1729/mqtt-error

Update WIT to match those in Spin

wit/mqtt.wit

@@ -5,8 +5,8 @@ interface mqtt {
         invalid-address,
         /// There are too many open connections
         too-many-connections,
-        /// A retrieved value was not of the correct type
-        type-error,
+        /// Connection failure e.g. address not allowed.  
+        connection-failed(string),
         /// Some other error occurred
         other(string),
     }
@@ -20,7 +20,7 @@ interface mqtt {
 
     resource connection {
       /// Open a connection to the Mqtt instance at `address`.
-      open: static func(address: string, username: string, password: string, keepaliveinterval: u64) -> result<connection, error>;
+      open: static func(address: string, username: string, password: string, keep-alive-interval-in-secs: u64) -> result<connection, error>;
 
       /// Publish an Mqtt message to the specified `topic`.
       publish: func(topic: string, payload: payload, qos: qos) -> result<_, error>;