Add tax_term and posts_per_page to [sermon_images] like we have for [sermons]

[Allen Cox]

Direct quote from the suggestor, [e-mail]

"Hey I was in your readme file while looking at tweaking the code for my church and I was thinking the [sermon-images] having the additional options of taxonomy and tax_term like the [sermons] shortcode does as well as posts_per_page. Both of these would have been helpful to me today in laying out a series archive for my church (only including our adult venue and limiting it to the most recent number so I could arrange them in column next to our standard [sermon] shortcode for the most recent ten sermons. This might not apply to everyone, but since your readme file said you welcome requests I thought I'd send it out in case you wanted to put it in a future release. :-)"