French translations fixes

Changed "Hum" and "Swing" to better fit their original meaning.

• Swing should stay the same as english because we use the same word for golf swings, which the sound is inspired of.
  Also, "balançoire" is the swing that kids play on, which looked very funny.
• Hum became "bourdonnement", closer to drone. I think it fits better since we don't use hum in that context (humming).
• I added my name and e-mail to the contributors list at the start of the file.

Let me know if any other change needs to be made for the merge.