jjmccollum/teiphy: New options and better support for tabular outputs

In this release, teiphy's options for tabular outputs (in CSV, TSV, and Excel format) have been expanded and better organized. The type of tabular output desired can now be specified on the command line with the --table flag. Valid options are matrix (the default option, with rows for variant readings, columns for witnesses, and frequency values in cells), distance (a pairwise distance/dissimilarity matrix with rows and columns for witnesses and counts or proportions of disagreements at extant variation units in cells), nexus (with rows for witnesses, columns for variation units, and reading IDs in cells), and long (a series of rows with witness, variation unit ID, reading index, and reading text entries). Notably, --table long replaces the old --long-table command-line flag. A fix has been added to ensure that Unicode CSV and TSV files are loaded correctly in Excel. Finally, teiphy will now create directories in the output filepath if they do not already exist.