Create example with uploading multiple data points

[mgifford]

I was searching around about how to add different identifiers for http://pachube.com/feeds/30187 and I had a lot of trouble finding it. Eventually I found a reference with multiple data points & I was fine. Having a slightly more complicated example of how to upload the data would be useful in the docs.

I'm still stumbling around with pachube and having a php library like this is very helpful for me. Having so many examples in Perl isn't all that useful to me personally.