More tests needed for meshes with a broader range of element orientations

[fluidnumerics-joe]

This issue was discovered in PR #53

Our tests at the moment only cover simple meshes with element-neighbor orientations that have a flip of 0. This is leaving out some conditionals in the SideExchange calls that are left unverified. We ought to identify some test cases that use meshes that help us touch on other element-neighbor orientations.