Fixing SoundEffect.Play so that it sends the default pitch in Xna, 0.0f.  The old value of 1, caused extremely high pitched sounds in Xna on iOS and SoundEffectInstance already uses 0 as the default.
Merge pull request #1493 from nickdarnell/develop

Fixing SoundEffect.Play so that it sends the default pitch in Xna, 0.0f....