Allowing more pages be searched

[Eph97]

I've really enjoyed using the p command to search through a bunch of pdfs. However, I often wanted to search more than the default 2 pages. I added an optional flag -n that still defaults to 2 pages but allows the user to also choose to search more pages if desired.

Of course the recommended p function would also need to be modified to take advantage of this but most users would likely be able to figure out how to do this.

[bellecp]

I do not see how the cache is handled. If the output for pages 1-2 only is cached, and then pages 1-10 is requested, the result will be misleading or arbitrary with the current code.

[Eph97]

yeah, on my end, I handled that in the p function where if the -n option was different from the one used before then I ran a -clear-cache. I suppose it could also be handled inside the main.go file but I'd have to think about how best to do it.

If you think merging this feature is worthwhile I could try to think through how to handle the cache.