Fix encoding issue when using assert_requested during test runs where images have been uploaded.

[adamgaynor]

[bblimke]

@adamgaynor thank you. The change looks useful, though I'm not sure if modifying request_signature objects is a good idea, just because printing the signature failed.

[adamgaynor]

@bblimke It looked like modifying the request_signature was the simplest way to allow webmock to function again and properly analyze requests, when writing tests. Even if there were a way to properly print the signature, you'd end up with an enormous wall of encoded image (in this situation). I've been using a branch with this change for my own project.

[oliakremmyda]

Sorry but the issue is not so clear to me, @adamgaynor can you please add an example on the description or/and a couple of specs to document it? Thank you