[Bro-Dev] Doc generation tests fail

[Jonathan Siwek]

> Do we want to test Sphinx setup on NMI B&T? That adds a bunch more dependencies on all of these targets?

It should just be adding 1 dependency on Sphinx to the relevant target (currently `make doc`, but that will probably be subdivided into smaller targets per earlier discussion).  And it should be possible to just use easy_install to install Sphinx into the home directory.  Doesn't seem like a huge hassle to do it on NMI.

- Jon