Updated Grow with special dog height

Updated grow() to grow an extra amount of space to show the weightInput
when Dog is selected.

Bug currently exists where having multiple animalObjects of different
types causes strange behavior.
Fixed bug with multiple animalType objects

Bug was caused by variable not being in correct area of the scope, and
thus not reset when the function was re-run,. This was not an issue with
the selector, as previously thought.
animalWeight changes

animalWeight validation to make sure it is within a reasonable range,
that it isn't negative or zero, and that it doesn't allow letters. (In
Progress)

Minor CSS change to hide the up and down arrows next to the animalWeight
input field (may not be hidden on IE)