Changed logging errors to warning when losing markers or samples.
Removed superfluous import
Replaced band_pass w/ the more general filter

* updated docs
* updated and renamed test
* updated examples
Renamed filter to lfilter to avoid accidental collision with filter builtin

* changed unittests, docs, examples
Don't test for axis etc. if data is empty.

* Added test.
Added clear_markers

* plus docs and tests
Use clear_markers in RingBuffer

* updated tests
Added clear_markers to BlockBuffer

* added test
Fixed ringbuffer with clear_markers