default fast CWT test fails

[alsauve]

The current implementation of pywavelets CWT does not produce results in sync with the fast cwt implementation of this package.

As the fast CWT code was merged in pywavelets, the default fast transform code should be now the version of the pywavelets package.

• Unit tests output:

$ python3 unittests.py 
.F.
======================================================================
FAIL: test_fastcwt (__main__.Test_wfun)
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Traceback (most recent call last):
  File "unittests.py", line 31, in test_fastcwt
    self.assertLess(np.std(np.abs(coef1-coef2)), 1e-12)
AssertionError: 0.07116417974643739 not less than 1e-12

----------------------------------------------------------------------
Ran 3 tests in 0.224s

FAILED (failures=1)