Enhanced documentation and code clean ups
Converted DateTime doc to html
Implemented PeaksAndValleysVisitor visitor
Implemented EhlersHighPassFilterVisitor visitor
Implemented EhlersBandPassFilterVisitor visitor
Implemented reading/writing in binary format
Implemented reading binary data format in chunks
Implemented serialize() and deserialize()
Implemented reading/writing containers in binary format
Added optional time-zone to strings parsed by DateTime constructor
Implemented PowerFitVisitor visitor
Implemented QuadraticFitVisitor visitor
Implemented fill_policy::lagrange_interpolate
Implemented correlation_type::kendall_tau
Implemented change_freq()
Implemented duplication_mask()