Test search by file name function

[gatukgl]

• I've renamed test assets at the root directory from images to be test-assets and also added some images there.

• I've added jest to run unit tests for .search() in index.js. So now we can use a command $ yarn test:jest to run unit tests.

• For the index.js, to run unit tests against this file. I've checked running environment if there's test environment, we could just interested in .search() or .format()

**This PR includes just the tests for .search(). I'll added another PR for .format() if it's done.

If there's any question. Feel free to ask me. :)

connected to #12

[gatukgl]

This PR includes just the tests for .search(). I'll added another PR for .format() if it's done. :D

[btk]

Hey @gatukgl this is great. I merged this and added babel presets to package.json also changed the npm script tags. And added info about how to use test scripts, see current master.

Thank you!