Roll backbone

[jacob-morrison]

Changes proposed in this pull request:

• Rolling and unrolling dimensions in the VilBERT backbone

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[dirkgr]

Just one question: Why repeat_interleave()?

[dirkgr]

Let me know when this is ready to be looked at again?

[dirkgr]

Looks good. I assume there is a corresponding change in the models repo somewhere that changes how your reader operates, correct?

[jacob-morrison]

Looks good. I assume there is a corresponding change in the models repo somewhere that changes how your reader operates, correct?

Yup! I already changed my nlvr2 reader to work with these changes; I'm training that model again now and then I'll be able to send out that PR as well.