Add check for large committed files
People sometimes commit data files to git repos that are unreasonably large, particularly files that might be generated in the process of a notebook getting executed. The check_nbs script in nbpages should be updated to have an option to allow this, which can then be enabled here.
I wanted to take a try at this. What size would be considered large? Or should we just check for file extensions other than what is needed instead of looking at size? We could also possibly implement this using just the gitignore file to ignore common data file types that may be committed. This would discourage notebooks including/depending upon data files.
@obviousrebel , @eteq has some suggestions over at https://github.com/spacetelescope/style-guides/blob/master/guides/where-to-put-your-data.md
Closes with merge of https://github.com/eteq/nbpages/pull/8 (WIP)