Update docs on what to use instead of showall

[mauro3]

showall is gone: JuliaLang/julia#22847 How to best look at results now? Note that repr and print show even less info.

[devmotion]

I was wondering the same and noticed that show(stdout, MIME"text/plain"(), suite) displays only a limited and non-verbose summary. For a more verbose output one has to provide the verbose and limit keywords, see https://github.com/JuliaCI/BenchmarkTools.jl/blob/master/src/groups.jl#L253). In my opinion it would be nice if BenchmarkTools would respect common properties of IOContext such as limit and compact.

[jrevels]

Yup, BenchmarkTools was originally written before we had the nice IOContext interface. It'd be great for BenchmarkTools to be updated to properly respect it.