Fix wrong usages of API in Example 1

[dobachi]

I propose a few fix about the document.

• Change to use ExcelReadRowCol instead of ExcelReadCell to use the row and column number to specify the cell.
• According to the example image of Excel, the row number should be 1
• If we don't provide enough number of words, the list loolup_words includes None. These None causes exceptions in the later part. This is why, I inserted a procedure to remove None from it.
• Change to use ExcelWriteRowCol instead of ExcelWriteCell. The same reason with the above.