TST: fix test failure due to usage of float128, which isn't always present.
TST: fix stats.gmean/hmean test failures due to copy-paste error.

Not noticed before because TravisCI numpy doesn't have float96.
TST: silence DeprecationWarning's for interpolate.PiecewisePolynomial
BUG: fix PPoly.roots for indexing bug with ellipsis in numpy 1.6.0
TST: fix issue in optimize test with comparing infs (was failing with 1.6.0).
TST: fix DeprecationWarnings with numpy 1.8.0 in signal.savgol_coeffs().