Matched filter update

The matched filter so far only used the templates we have provided at two sampling rates but it should really take a template as an argument so that the user can supply the template. If the user omits the template argument it still tries to load the pre-defined templates from the templates folder. However, that's more for backwards compatibility.

r_peaks = detectors.matched_filter_detector(unfiltered_ecg,"templates/template_250hz.csv")