Fix AreaDefinition usage to work with newer versions of pyresample

[djhoese]

AreaDefinitions argument names have changed. A lot of my usages of AreaDefinition specified x_size and y_size but these have been changed to width and height in pytroll/pyresample#138 to match the areas.yaml format. This PR fixes all uses of those arguments by name.

This PR should probably only be merged after that pyresample PR is merged and released to be sure I fixed everything.

• Tests added
• Tests passed
• Passes git diff origin/master -- "*py" | flake8 --diff

[coveralls]

Coverage increased (+0.01%) to 77.445% when pulling 2f96ca3 on djhoese:bugfix-new-resample into 417b29f on pytroll:master.

[codecov]

Codecov Report

Merging #554 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #554      +/-   ##
==========================================
+ Coverage   77.43%   77.44%   +0.01%     
==========================================
  Files         136      136              
  Lines       19143    19153      +10     
==========================================
+ Hits        14823    14833      +10     
  Misses       4320     4320

Impacted Files	Coverage Δ
satpy/tests/writer_tests/test_mitiff.py	95.55% <ø> (ø)	⬆️
satpy/readers/hrit_jma.py	98.43% <ø> (ø)	⬆️
satpy/tests/writer_tests/test_scmi.py	97.08% <ø> (ø)	⬆️
satpy/tests/test_resample.py	98.89% <ø> (ø)	⬆️
satpy/tests/test_multiscene.py	94.33% <ø> (ø)	⬆️
satpy/readers/geocat.py	91.72% <ø> (ø)	⬆️
satpy/tests/reader_tests/test_utils.py	75.89% <ø> (ø)	⬆️
satpy/tests/test_scene.py	99.32% <100%> (ø)	⬆️
satpy/scene.py	84.13% <0%> (+0.06%)	⬆️
satpy/readers/__init__.py	94.46% <0%> (+0.07%)	⬆️
... and 2 more

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[djhoese]

I tested this with the current pyresample master in a separate branch and all tests pass. That means that current tests pass with both the old version of pyresample and the soon-to-be-released version of pyresample.