Extracted the WebUpdate example into a library.

This ESP8266HTTPUpdateServer can be instantiated and used
more cleanly, it's also able to take or create an ESP8266WebServer
to configure the events and /update handler.

It's been made more robust by handling upload abort, which
depends on fix provided for issue #833

libraries/ESP8266HTTPUpdateServer/examples/WebUpdater/WebUpdater.ino

@@ -0,0 +1,43 @@
+/*
+  To upload through terminal you can use: curl -F "image=@firmware.bin" esp8266-webupdate.local/update
+*/
+
+#include <ESP8266WiFi.h>
+#include <WiFiClient.h>
+#include <ESP8266WebServer.h>
+#include <ESP8266mDNS.h>
+#include <ESP8266HTTPUpdateServer.h>
+
+const char* host = "esp8266-webupdate";
+const char* ssid = "........";
+const char* password = "........";
+
+ESP8266WebServer httpServer(80);
+ESP8266HTTPUpdateServer httpUpdater;
+
+void setup(void){
+
+  Serial.begin(115200);
+  Serial.println();
+  Serial.println("Booting Sketch...");
+  WiFi.mode(WIFI_AP_STA);
+  WiFi.begin(ssid, password);
+
+  while(WiFi.waitForConnectResult() != WL_CONNECTED){
+    WiFi.begin(ssid, password);
+    Serial.println("WiFi failed, retrying.");
+  }
+
+  MDNS.begin(host);
+
+  httpUpdater.setup(&httpServer);
+  httpServer.begin();
+
+  MDNS.addService("http", "tcp", 80);
+  Serial.printf("HTTPUpdateServer ready! Open http://%s.local/update in your browser\n", host);
+}
+
+void loop(void){
+  httpServer.handleClient();
+  delay(1);
+}