Switch python-hdf4 dependencies to pyhdf

[djhoese]

As discussed in pypi/warehouse#5157 the python-hdf4 package has now been renamed and taken ownership of the pyhdf package. There is now no need to depend on the python-hdf4 package at all. This PR switches any remaining uses of python-hdf4 for pyhdf.

This only affects setup.py so no tests or doc changes needed.

[coveralls]

Coverage remained the same at 78.079% when pulling a5fabe2 on djhoese:deps-pyhdf into f3358ca on pytroll:master.

[codecov]

Codecov Report

Merging #647 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #647   +/-   ##
=======================================
  Coverage   78.07%   78.07%           
=======================================
  Files         137      137           
  Lines       19890    19890           
=======================================
  Hits        15530    15530           
  Misses       4360     4360

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f3358ca...a5fabe2. Read the comment docs.