Add 10-using-rollup-with-gulp.md with example code for integrating with gulp.

src/guide/10-using-rollup-with-gulp.md

@@ -0,0 +1,31 @@
+---
+title: Using RollupJS with Gulp
+---
+
+Rollup returns promises which are understood by gulp so integration is easy.
+
+The syntax is very similar to the configuration file, but the properties are split across two different operations. Constructing the bundle, and transpiling to a target output.
+
+```js
+var gulp = require('gulp')
+    rollup = require('rollup')
+    rollupTypescript = require('rollup-plugin-typescript')
+;
+
+gulp.task('build', function () {
+  return rollup.rollup({
+    entry: "./src/main.ts",
+    plugins: [
+      rollupTypescript()
+    ],
+  })
+    .then(function (bundle) {
+      bundle.write({
+        format: "umd",
+        moduleName: "library",
+        dest: "./dist/library.js",
+        sourceMap: true
+      });
+    })
+});
+```