A few spelling/grammar/typo tweaks

Hi Pablo
I found the minifesto via twitter and think it's a great piece of work - thanks for writing it! While reading I spotted a few minor typos etc so thought I'd submit a pull request with some tweaks... Also the 'shorter letter' quotation seems to be originally by Pascal not Pasteur, but perhaps the true origin is so unclear it doesn't matter!

Thanks again for writing this - I hope the pull request is useful.
Richard