MAINT: Python3 classes do not need to inherit from object

[mwtoews]

See this Q/A for a background on class Foo(object): vs class Foo:.

In summary, only Python 2 required inheriting from object, but this is no longer necessary with Python 3 (and the docs don't use that style here or here). This PR keeps the base classes a bit tidier and quicker to identify.

Edits were automated using:

git ls-files -z | xargs -0 sed -i -re 's/class (.*)\(object\):/class \1:/g'

[codecov]

Codecov Report

Merging #2025 (d110fe4) into master (1d569e6) will not change coverage.
The diff coverage is 92.30%.

@@           Coverage Diff           @@
##           master    #2025   +/-   ##
=======================================
  Coverage   89.90%   89.90%           
=======================================
  Files          17       17           
  Lines        2307     2307           
=======================================
  Hits         2074     2074           
  Misses        233      233           

Impacted Files	Coverage Δ
h5py/_hl/dataset.py	93.14% <66.66%> (ø)
h5py/_hl/base.py	96.18% <100.00%> (ø)
h5py/_hl/group.py	96.78% <100.00%> (ø)
h5py/_hl/selections.py	87.50% <100.00%> (ø)
h5py/_hl/selections2.py	97.61% <100.00%> (ø)
h5py/_hl/vds.py	96.55% <100.00%> (ø)

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[takluyver]

Thanks - I'll merge this. I think the benefit is a bit borderline, though. If you're thinking of doing more cleanups, it might be worth asking before making a PR.