Adds Travis CI Build Status badge

[ivanseed]

Fixes #221

• [x] Pull Request Title is of form Problem Code (Contest Code) [Language].
• [x] This problem already had an entry in this repository.
  • [x] This solution is better than the one already in this repository.
• [x] This solution is prepared by me and not copied from anywhere else on the web.
• [x] I have added a copyright comment in my solution.
• [x] I have updated README.md file (in appropriate order).
• [x] I have read and followed Code Samples.
• [x] I understand that pull request will be closed if I failed to update it even once in a week.

[aashutoshrathi]

Hi! Thanks for contributing to this repository. Make sure you have checked points in PR correctly.