allow creating pdf from byte arrays

[lefnire]

you might add some options{} parameter to be passed in to your initialize(), image(), etc. functions that allow configurable sources (rather than everything coming from a path on the file-system).
For example, I only had to change a couple lines of code to allow the input to come from byte[]:

reader = @pdfreader.new_with_sig("[B", pdf_bytes)

img = image._invoke('getInstance', '[B', image_bytes)

just some way so we can call an overloaded version of your iText function-calls

[jaywhy]

I think you can pass a byte array to the initialize method already, since it just passes the value to iText. This just needs to be documented.

As for the ability to pass byte arrays to the image method, etc., that is a good idea. I'm back in iText land lately. I'll add those changes. And… Only now did I realize this message is three years old. Whoops.