Bugfixes in the Electro-L reader

[simonrp84]

Ernst made a bug report in the google group: https://groups.google.com/forum/#!topic/pytroll/Dvvp9z2bIdc
Stating that he could not process or save images from the Electro-L satellite. This was for two reasons:

1. In the satpy/etc/readers/electrol_hrit.yaml the sensor was incorrectly named electrol rather than msu-gs.
2. A call to map_blocks in the calibration routine was not passing the look-up table, meaning that a TypeError: _getitem() missing 1 required positional argument: 'lut' was being raised.

This PR fixes both of these problems by adding the correct sensor name and by passing lut to the `_getitem" call.

• Closes https://groups.google.com/forum/#!topic/pytroll/Dvvp9z2bIdc
• Tests passed
• Passes git diff origin/master -- "*py" | flake8 --diff

[djhoese]

Looks good to me and I see why the map_blocks was failing. My fault, so thanks for fixing it.

I think in the long term we should consider renaming the reader since electrol is technically the satellite and not the sensor (even though OSCAR lists the sensor as "Electrol Imager").

[codecov]

Codecov Report

Merging #726 into master will increase coverage by 0.42%.
The diff coverage is 96.52%.

@@            Coverage Diff             @@
##           master     #726      +/-   ##
==========================================
+ Coverage   80.02%   80.44%   +0.42%     
==========================================
  Files         147      148       +1     
  Lines       21498    21612     +114     
==========================================
+ Hits        17203    17385     +182     
+ Misses       4295     4227      -68

Impacted Files	Coverage Δ
satpy/readers/electrol_hrit.py	92% <100%> (+57.6%)	⬆️
satpy/tests/reader_tests/__init__.py	97.77% <100%> (+0.05%)	⬆️
satpy/tests/reader_tests/test_electrol_hrit.py	96.46% <96.46%> (ø)

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[coveralls]

Coverage decreased (-0.005%) to 80.017% when pulling ba2f3f2 on simonrp84:master into 1849b17 on pytroll:master.

[coveralls]

Coverage increased (+0.4%) to 80.423% when pulling 085e472 on simonrp84:master into 1849b17 on pytroll:master.

[mraspaud]

Lgtm, feel free to merge!

[mraspaud]

LGTM