French translation update
Took advices and changes from pull request 77 into account
https://github.com/gothfox/Tiny-Tiny-RSS/pull/77
Merge branch 'master' of git://github.com/RaphaelRochet/Tiny-Tiny-RSS into RaphaelRochet-master

Conflicts:
	locale/fr_FR/LC_MESSAGES/messages.mo
	locale/fr_FR/LC_MESSAGES/messages.po
rebase translations