def add_table(name, table)
      if table.is_a? Hash
        tables[name.to_sym] = table
      else
        raise TypeError, 'Invalid table format' 
      end     
    end
def add_table(name, table)
      if table.is_a? Hash
        tables[name.to_sym] = table
      else
        raise TypeError, 'Invalid table format' 
      end     
    end
Adds a table to the table store. A valid table must be a Hash with single character string keys and numerical values.
 A table that is not a Hash will raise a TypeError. The table name will be converted to a Symbol.
 @example
   Gematria::Tables.add_table :mini_english, 'a' => 1, 'b' => 2, 'c' => 3
 @raise [TypeError] if table is not a valid Hash
 @param name [#to_sym] table name
 @param table [Hash{String => Number}] table of characters pointing to corresponding values
 @return [void]