move memory tests, add base perf tests

not so impressive perf results. a lot work to do …
fix readme
improve perfomance
perf tests, some optimizations
add some perf tests
optimize multiple-source streams
:sparkles: SEO :sparkles:
refactoring
fix readme
minor refactoring
minor fix
refactor perf tests
readme
refactoring
refactoring
add `.publish().refCount()` to base Rx streams in perf tests

it will be more fair and correct, if I understand correctly Rx docs
fix .filter()
bunch of minor changes
minor
various small fixes and optimizations