Fix failing tests 2

[cvle]

This PR focuses on the current Firefox browser v51 and including the PRs I sent over at autoprefixer and caniuse db will let it pass the test suite.

• Excludes column-span for firefox from test suite
• Excludes mask-* props for older firefox from test suite
• Supports former break-* props for firefox
• Supports non standard break-* props for webkit browsers

[cvle]

Less than 107 failing cases left :-)

[kof]

Looks good, just the double quotes.

[cvle]

Alright, added linting for the test folder

[kof]

merged!