Add Travis CI

[vietlq]

Scope:

• Test cases
• pip dependencies
• Support for various Python versions
• Pylint
• Style guide

[vietlq]

@luongnt95 I already added Travis CI for my fork and currently support style guide with Flake8: https://travis-ci.org/vietlq/oyente/jobs/371942593

Feel free to merge the PR and keep this issue open as I will keep adding:

• Test cases
• pip dependencies
• Support for various Python versions
• Pylint

[vietlq]

Bots for consideration:

• https://github.com/bluzi/travis-buddy
• https://github.com/barosl/homu

[yxliang01]

320 has been merged. Is this issue still relevant? @vietlq