Fix deprecation warnings from openpyxl
Fix deprecation warnings from openpyxl

This change fixes two deprecation warnings:

    DeprecationWarning: Call to deprecated function get_sheet_names (Use wb.sheetnames)
    DeprecationWarning: Call to deprecated function get_sheet_by_name (Use wb[sheetname]).
psnj/petl,alimanfoo/petl,Marketing1by1/petl