cleaned up gitignore thanks to new git releases

Not as shiny as some of the other cool projects, but I figured it was worth it. Thanks to newer versions of git, recursive glob patterns work, which allowed me to remove redundant lines from the gitignore file.

I tested this by creating a dummy git repo with similar ignore patterns and adding/removing files and directories. I also ran a `make` and `make pdf` to see if generated files were ignored properly.

If someone could do additional testing, I'd appreciate it, but I don't *think* I broke anything.