Error in Travis CI build check configuration

[rishiraj]

The requirement Biopython requires Python 3.6 or later however Python 3.5 is configured in Travis CI build check hence it is wrongly failing all valid Pull Requests.

[Priyatham-sai-chand]

Fixed and sent the PR #16 . You may close this issue.
I didn't see any code breaking changes after making it 3.6. Make a new issue if you find some. So, we can figure it out.