fixed tanh to not return NaN for input values outside the range [-40, 40]
Fixed header order to satisfy linter
in SoftmaxLossLayer, check label >= 0 in addition to upper bound
use DCHECK in SoftmaxLossLayer so that bounds checking has no perf penalty without DEBUG
Merge pull request #1469 from longjon/label-lower-bound

Check both lower and upper bounds in SoftmaxLossLayer
Merge pull request #1455 from seanbell/tanh-fix

Fix tanh layer for badly scaled input values