The new range handling method will raise ValueError for arrays including NaN

This issue appears after one of the latest changes to function_base.py (around Row 550 in 127eb9e on March 16, 2016). Resetting the range to array minimum and maximum by using a.min() and a.max() will raise ValueError: 'range parameter must be finite.' if the array includes NaN. Before the change, the codes assigned a pair of range parameters only when they were included in the input explicitly.
