First draft for the French translation of lesson 1

I was unsure about how to translate the code samples, and IDLE menu
names. I went with the following:
 * IDLE menu names are left in English since they don't seem to
   have a French translation in IDLE
 * Variable names and method names are left in English to avoid
   confusion that could be caused by having code written in two
   languages
 * Copy in the code is translated to French ("Hello world" becomes
   "Bonjour tout le monde")
Merge pull request #28 from VivienBarousse/fr-FR

French translation of lesson 1