adjust acct settings nav to account for margin delivered from top-level main element now.
adjust acct settings nav to account for margin delivered from top-level main element now.

also gets rid of annoying and messy negative margins by using box
shadows instead of borders. borders are singular and alter an elements
box-model, box shadows are infinite and do not alter box-model

RayRutjes/frontend,circleci/frontend,prathamesh-sonpatki/frontend,circleci/frontend,RayRutjes/frontend,circleci/frontend,prathamesh-sonpatki/frontend