re-org code to experiments namespace

[scttl]

Typical python package practice is to import relative to some top-level namespace and to put all the modules under a subdir of the same name. Right now this project has one module named lib that is installed directly, however this name isn't exactly informative and if we later add other modules to the package they will end up scattered across different directories.

Instead we should put all modules under a new experiments subdir. Note that this change will break existing imports e.g. from lib.exp import Client needs to become from experiments.lib.exp import Client