OrderedHash#insert_before and #insert_after are not used

[jcoyne]

They are only referenced by specs. Do we need them?

[jpstroop]

I added them because the IIIF spec implies a certain order for the keys, and make it easier to keep keys in a preferred order.

[jcoyne]

Who is the consumer?

[jcoyne]

If order is very important, I wonder if we wouldn't be better off modeling this as a list of tuples instead of a Hash.

[jpstroop]

That's where I started, actually, and then found myself writing a lot of methods I knew I could get from OrderedHash, but I'm open to it.