Remove src/bin/perf.rs or move it somewhere else

[ignatenkobrain]

Unfortunately this makes cargo install flume to install perf binary which would override system perf coming from linux kernel..

Would be nice if you could move it to tests, examples or somewhere else.

[zesterer]

We're reworking the internals of Flume at the moment, so we'll be removing it soon. Thanks for opening an issue!