Improvements to RandomMutantSelectionStrategyTest

[DurieuxPol]

Fixes #35, fixes #36, fixes #37
Reworked RandomMutantSelectionStrategyTest to have better tests. Added = method for MethodMutation in this regard.
Added as well hash method, so that two MethodMutation instances that are equal according to = have the same hash code (that was not the case before).

[coveralls]

Pull Request Test Coverage Report for Build 7223043196

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A quick fix for this PR: rebase it; your next report should be accurate.

• 55 of 55 (100.0%) changed or added relevant lines in 3 files are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+1.0%) to 60.361%

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Files with Coverage Reduction	New Missed Lines	%
src/MuTalk-Model/MutationTestingAnalysis.class.st	4	61.44%

Totals
Change from base Build 7193015466:	1.0%
Covered Lines:	3851
Relevant Lines:	6380

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💛 - Coveralls

[guillep]

Hi Pol, there are some improvements to do here before integration!

[guillep]

Thanks!!