CHANGES FOR VERSION 2.2.0
------------------------
    o Added checks to avoid producing identical matrices or data frame when the
    parameters are still the same after first function call.
    o Splitted the analysis in multiple (optionnal) intermediate steps
    (add_design, produce_matrices and produce_data_frame).
    o narrowPeak and broadPeak format is now supported.
    o Added multiple getter to access metagene members that are all now
    private (get_params, get_design, get_regions, get_matrices,
    get_data_frame, get_plot, get_raw_coverages and get_normalized_coverages.
    o Added the NCIS algorithm for noise removal.
    o Replaced the old datasets with promoters_hg19, promoters_hg18,
    promoters_mm10 and promoters_mm9 that can be accessed with
    data(promoters_????).
    o Added flip_regions and unflip_regions to switch regions orientation based
    on the strand.