Add CI to check if pull request breaks rules of Sudoku

[xiegeo]

Idea:

When a pull request is made, CI can check for the basic rules of Sudoku, to flag any broken rules of uniqueness per rows, columns, and blocks.

The tests must use the table in the readme as the only source of truth. Tests may require formatting rules.

The tests should also be runnable locally.

The tests can use any programing environment. Having a test in one environment does not exclude making the same test in a different environment. The target is to have any developer commit sudoku in their favorite environment.

Tests must not play Sudoku for you, or take away the fun.

Please add your forks here if you decide to implement such tests.

Working and Todos:

• [x] Go tests with travis ci.
• [ ] Add others.

[xiegeo]

Started working on a go branch.