style: New UI created; feat: Backspace added; fix: Rendering issue re…

[shantanu0323]

…solved

1. UI improvised
2. Backspace feature added
3. added the required dependencies to resolve the rendering problems

Please make sure these boxes are checked before submitting your pull request - thanks!

• [✔] Run the unit tests with ./gradlew check to make sure you didn't break anything

• [✔] If you have multiple commits please combine them into one commit by squashing them.

[mayank-kgp]

• If you would like to work on any issue, then please comment on that issue that I would like to work on this. It will also give you a chance to check that whether anyone else is working on the same issue or not. If no one is working on that issue then you can work on that.

• You should send separate PR for the different issues. There is no point of sending a single PR for multiple issues.

• Go through this discussion - https://gitter.im/VoiceCalculator/discussion?at=5a26b7c5c65707ba2b154bad