Added Linear Search [C#]

[DimaMukhin]

Fixes #470

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[singhpratyush]

Hi! Thanks for showing interest in contributing to this repository.

Please make sure that you have ticked the points mentioned in PR description correctly.

Thanks again!

[aashutoshrathi]

@singhpratyush The Travis Build is failing due to spacing in comments, can this be ignored?

[Monal5031]

@aashutoshrathi No, it will cause other PRs to fail too.

[DimaMukhin]

Is there a way to test commits with Travis without committing?

[Monal5031]

@DimaMukhin For spacing/indentation issues you can test locally using coala.