Add --ignore-newlines option

[pferreir]

I apologize for opening a PR directly, but this was simple enough that it would be easier to explain it with an actual example.
This is an attempt at solving the issue described in djrobstep/schemainspect#33. I'm adding an --ignore-newlines option as suggested by @djrobstep, which is propagated down to the function comparison function (done by djrobstep/schemainspect#37).

I'm willing to improve the PR, if you wish to follow this route.

[gregplaysguitar]

Thanks for making a start on this! IMO this would be better named --normalise-newlines, since newlines are still significant to the comparison, they're just normalised to a standard entity.

[djrobstep]

Yep, I agree that normalise is more accurate as a description

[ThiefMaster]

what about normalize? I think in almost all other programs CLI options use the en_US versions, so users are likely to get it wrong if migra expects en_GB

[djrobstep]

Yep, -ize definitely the preferred spelling