Deprecation warning for frechet_l and frechet_r in tests

[jfinkels]

Looks like this:

[...]/goftests/test.py:203: DeprecationWarning: `frechet_l` is deprecated!
The distribution `frechet_l` is a synonym for `weibull_max`; this historical
usage is deprecated because of possible confusion with the (quite different)
Frechet distribution.  To preserve the existing behavior of the program, use
`scipy.stats.weibull_max`.  For the Frechet distribution (i.e. the Type II
extreme value distribution), use `scipy.stats.invweibull`.
  samples = self.dist.rvs(*param, size=sample_count)

Similar deprecation warning for frechet_r.
(See also issue #19.)