Add tests and coverage

[rishacha]

Implements #130

Status :

Just started a PR. I have checked in the following fix -

[01:33:16] gulp-notify: [Compile Error] Cannot find module './Data' from '/home/rishacha/code/react-materialui-notifications/src/app'
[01:33:16] gulp-notify: [Error running notifier] Could not send message: not found: notify-send

fixed a minor typo in Main.js

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• [x] Make sure to make changes to one file per pr. NOTE : The build folder should be in .gitignore
• [ ] Make sure it passes all linter checks of the ci. To more about the linter rules go [here] (https://houndci.com/configuration). Pending
• [x] Be precise as to what are you trying to correct in your title and/or comment.
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• [x] Try to make as little changes as possible to make the diff more readable.
• [ ] Respect the coding guidelines as mentioned in the linter guide. Pending

[puranjayjain]

@rishacha thanks for your PR! ping back here when you are done 100%, if you think some hound and coding guidelines are skippable or ignorable please tell and we'll move forward with the merge