Clear up some confusion caused by AngularJS number filter

Implement `floor` rounding for Mana, so users don't get "Not enough Mana" errors for trying to spend 30 out of 29.8 points. (They'll see 29 instead of 30.) 

Implement `ceil` rounding for Health, so users don't look like they should be dead when they're at .3 HP. (They'll see 1.)

Implement `floor` rounding for Experience, so it doesn't look like the user ought to have leveled up when they're at 639.7 out of 640. (They'll see 639.)