Update peridot to 0.5.4 (ring-anti-forgery error)

[Frozenlock]

Some of my Kerodon tests fail with anti-forgery error.

I suspect it's related to how the URLs are built (http://localhost:2000/my-url vs /my-url) before visiting them. https://github.com/xeqi/peridot/commit/4cb7747bec761695340f2b2fd8601cf58d561e7c

But anyway, this is solved by bumping the Peridot dependency to version 0.5.4.

[danielcompton]

Hey, I tried bumping the version but it broke a bunch of other tests, I think because of the transitive dependency upgrade on ring-mock. If you want to do the work to upgrade Peridot and fix the tests that would be great, otherwise I'll get to this someday.

[Frozenlock]

Sure, I'll try to take a look early this week.