feat(flatten): Implement variable arity for flatten function, add test

[davidrayoussef]

First PR. Added implementation for flatten function to accept multiple arrays, and added a test with multiple parameters.

[codecov-io]

Current coverage is 100.00%

Merging #18 into master will not affect coverage as of e467e3a

@@            master     #18   diff @@
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  Files            5       5       
  Stmts           18      18       
  Branches         0       0       
  Methods          0       0       
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  Hit             18      18       
  Partial          0       0       
  Missed           0       0       

Review entire Coverage Diff as of e467e3a

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[kentcdodds]

Fantastic. This is great. Thank you for your contribution! Could you update the commit message to more closely follow the standard? The subject is too long and it should state that it's closing #17
Thanks!

[davidrayoussef]

No, thank you Kent for helping me get my first green. But can you help me update the commit message? Should I do an npm run commit again? Because I'm getting an error since there are no changes. Or should I do a force push, or can I edit it right in Github?

[kentcdodds]

In this scenario, the easiest would be to run git reset HEAD^ then do git diff to make sure the changes are what you expect, then run git add -A and run npm run commit or you could create your message by hand with git commit

Let me know if you need more direction!

[davidrayoussef]

Okay cool. I think I got it right this time, but had to do a force push. Let me know if there's an issue.

[kentcdodds]

Perfect! Thank you! And congrats on your first pull request!