Fix typo (backgroud) in text function

[m42e]

No description provided.

[vadmium]

Looks good to me. Though I notice the rect() function has the same spelling error.

It looks like nobody tested setting the background field. I wonder if it would be okay to get rid of the *args and **kwargs parameters to these functions, which would make this kind of error more obvious.

[m42e]

Yes, I saw the rect has the same typo. But besides the typo the background is ignored anyhow, because no fillled box will be drawn. :X

I'm not sure is this just a plain 'copy' of the pho version or is further development here welcome?

Edit:
The Template is not part of the PHP fpdf, so I think it would be ok. Please let this unmerged, and I'll have a closer look at it.

[m42e]

Fixed within #74.