Squirrel Search Algorithm implementation try

[altaregos]

Summary

Squirrel Search Algorithm implementation under ssa.py. The code does not have any bugs but the algorithms accuracy needs to be checked. Open Issue #338

[firefly-cpp]

Thank you @altaregos for your implementation.

I ask @zStupan to be reviewer of this implementation.

[firefly-cpp]

@altaregos, please add at least one test file as well as one example.

See examples:

DE tests

DE example