Documentation fixes (mostly in Tutorial)

I'm hoping to work my way through the rest of the documentation eventually, but I decided to start with the Tutorial since it's a section that I imagine quite a few people read through.
"Web 2.0" itself is a proper noun (see its usage in its [Wikipedia article](http://en.wikipedia.org/wiki/Web_2.0)) so I think it would more appropriate to leave the `W` capitalized.