Feature/style login pages

Hey there, this PR implements tracker story 67127028, [Style Account screens (Log In, etc.)](https://www.pivotaltracker.com/n/projects/890876/stories/67127028)

See the related [IOS PR](https://github.com/jmoody/wetap-ios/pull/69)
Equivalent for our purposes, but if we were developing for devices (e.g. android) it could be more flexible to target using min-height or max-height.