Create function to update h-card table given array of h-card URLs

[jacobwhall]

In a few different contexts, I'd like to check the sender's h-card against my contacts directory, and update it if necessary. See #9 for a description of what the contacts directory will look like.

[jacobwhall]

This function will need to predictably clean the URLs so that there aren't any accidental duplicates in the directory. This will involve following any redirects, and possibly removing any trailing slashes.