[build] added gulp builder

tasks/tail.js

@@ -0,0 +1,26 @@
+'use strict';
+const through = require('through2');
+const gutil = require('gulp-util');
+const col = gutil.colors;
+const Tail = require('tail').Tail;
+
+module.exports = (handler) => {
+    let stream = null;
+    let tail = null;
+
+    const bufferContents = (file, enc, callback) => {
+        tail = new Tail(file.path);
+        tail.on("line", handler);
+        callback();
+    };
+
+    const endStream = (callback) => {
+        if (tail) {
+            tail.unwatch();
+            tail = null;
+        }
+        callback();
+    };
+
+    return stream = through.obj(bufferContents, endStream);
+};