Correcting some typos and grammar in french translation.

Hi,

I was really happy to see a french translation of the manifesto. There was some little typos in the translation that I've corrected and submit to you.

I'm hesitate for also translating the title, in "Le manifeste du code" or "Le manifeste des codeurs", but, since, I can't agree with myself :grinning: , I prefer to let it in english.