Create a new video tutorial for Infowindow sizing with dynamic images/videos

[matallo]

Use the new width controller,

Video tutorial should be 2 parts.

1. Basic, just show how to add infowindows and increase the width.
2. Advanced, include a dataset with an image url in one of the columns. Use the width slider to fit the images. If you can think of a simple dataset with URLs for images or to create a dummy one, perhaps use the streetview example, http://blog.cartodb.com/post/84121955934/a-picture-is-worth-1-000-attributes-infowindows-with

[matallo]

also https://github.com/CartoDB/docs/issues/13