Suppress warning outputs during testing

[iuliadmtru]

Right now warnings that are generated by tests appear in the log messages. I think we can suppress them (since we intentionally test for them), it would be easier to read the logs.

[smishr]

Can #42 be used to solve this?

[smishr]

@iuliadmtru add a PR for this into singledesign branch.

[iuliadmtru]

This was mostly solved with #168, apart from three warnings: two coming from sturges and freedman_diaconis which I mentioned in this comment in the same PR, and one that is the last log when running julia make.jl:

┌ Warning: Documenter could not auto-detect the building environment Skipping deployment.
└ @ Documenter ~/.julia/packages/Documenter/48VFh/src/deployconfig.jl:75

I don't know how we can avoid this, or even if we can.

[smishr]

New SurveyDesign doesnt have warnings.