TST: fix issue in Wavelet2D node deletion test.

Issue was that the node that was deleted in the test did not yet exist.
BUG: return wavelet properties as string not bytes.  Closes gh-34.
TST: fix test for lazy evaluation of 2-D wavepackets.
MAINT: re-eanble float32 computations through fused types.

This is not faster, need to reconsider later whether this is actually useful.
MAINT: re-enable float32 for upcoef(), downcoef() and swt().
MAINT: make downcoef() accept array_like input.
Merge branch 'enable-float32' into master.

Closes gh-35
Closes gh-9
TST: add tests for centrfrq and scal2frq.
TST: add test for integral on orthogonal wavelet, intwave().
MAINT: minor cleanups in functions.py
Merge branch 'pr/37' into master.

See https://github.com/rgommers/pywt/pull/37
TST: adding doctests for thresholding as unit tests.
TST: add some tests with 2-D arrays for thresholding functions.
Merge branch 'pull-39' into master.

See https://github.com/rgommers/pywt/pull/39