Minor fixes in spelling and grammar

Hi Nishio,

Onegai Shimasu!

I thank you for sharing the early English translation draft of your successful book.
As a Brazilian I am not fully qualified to be a copyeditor or proof-reader for your book.
Nevertheless, I took the liberty of cloning the repository and submitting to you some minor corrections.

best regards,
Rod Senra
http://rodrigo.senra.nom.br