Fix yaml area loading when projection is latlong (units degrees)

[djhoese]

YAML parsing was assuming meters for units even for latlong projections.

@pnuu @wroberts4 Can you verify that this fixes the issue brought up on slack.

[djhoese]

Ok, I made this PR from pycharm. Starting to figure out how it works...hopefully this is the last time I make a branch on the main repository.

[coveralls]

Coverage increased (+0.009%) to 85.95% when pulling 1a947bb on bugfix-latlong-units into aba7897 on master.

[codecov]

Codecov Report

Merging #167 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #167      +/-   ##
==========================================
+ Coverage   85.97%   85.98%   +<.01%     
==========================================
  Files          37       37              
  Lines        6551     6555       +4     
==========================================
+ Hits         5632     5636       +4     
  Misses        919      919

Impacted Files	Coverage Δ
pyresample/area_config.py	86.74% <100%> (ø)	⬆️
pyresample/test/test_utils.py	98.65% <100%> (+0.02%)	⬆️

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