Added QuickSelect Algorithm

[achudinovskyh]

#14 I've added Quick Select algorithm

• Add an algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new JavaScript files are placed inside an existing directory.
• All filenames should use the UpperCamelCase (PascalCase) style. There should be no spaces in filenames.
  Example:UserProfile.js is allowed but userprofile.js,Userprofile.js,user-Profile.js,userProfile.js are not
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[marsonya]

Hey @achudinovskyh, this is great work. There's just one thing missing.
The Doctests. Kindly see CONTRIBUTING.md for details.

You may also refer this file.

[marsonya]

It's a good addition to our Codebase.
The doctests are missing though.
The tests can be added later since a lot of other algorithms too don't have tests as of now.