Add energy dispersion unit test

[LukasNickel]

No description provided.

[codecov]

Codecov Report

Merging #41 into rewrite will increase coverage by 3.93%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           rewrite      #41      +/-   ##
===========================================
+ Coverage    45.65%   49.58%   +3.93%     
===========================================
  Files           25       26       +1     
  Lines          587      609      +22     
===========================================
+ Hits           268      302      +34     
+ Misses         319      307      -12     

Impacted Files	Coverage Δ
pyirf/irf/tests/test_energy_dispersion.py	100.00% <100.00%> (ø)
pyirf/irf/energy_dispersion.py	100.00% <0.00%> (+70.58%)	⬆️

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[HealthyPear]

For the joy of @maxnoe

Warning, treated as error:
/home/travis/build/cta-observatory/pyirf/docs/changelog.rst:37:Title underline too short.

`0.1.0 <https://github.com/cta-observatory/pyirf/releases/tag/v0.1.0>`__ (2020-09-16)
-----

Error: Error building sphinx doc

[maxnoe]

Working on it 🤣

[HealthyPear]

Requirements

• Merge PR Start refactoring pyIRF #36

[maxnoe]

@HealthyPear This PR targets #36, so merging this will update #36, not the master branch

[HealthyPear]

@HealthyPear This PR targets #36, so merging this will update #36, not the master branch

Ah sorry I didn't realize it!

[maxnoe]

Thanks @LukasNickel