DraftJS Images Immutable?

[jnielson94]

It looks like there was a recent change to the main draft-js library that makes images consistently IMMUTABLE - facebookarchive/draft-js#2184. I'm not sure if that's something that should be changed in this library, or if we should adjust how we're handling things to account for the difference. We were using the same expected output for content created through draftjs and the converters in here and they don't match any longer (and if they're not going to that's fine, just wanted to ping and check).

Thanks!