Add tests

[jameswilson]

Any changes we make are really hard to test the impact without having an example to test with.

I suggest we create a sub-folder called test containing its own streamlined package.json, gulpfile.js, and a sass folder containing some simple sass rules.

As for how to properly write the tests themselves, I'm not sure. Maybe we should copy the generated contents of the css folder to other folder names like css-gulp-sass css-gulp-sass-no-sourcemaps etc and write javascript that recursively compares the generated output in css from running gulp sass and gulp sass --no-sourcemaps with these other folders.

Unfortunately though this wouldn't necessarily allow us to test things like purposeful linting failures.

It also wouldn't test to confirm BrowserSync commands work, so we'd need a separate test for that. Not sure how we'd write that either, to confirm that the watch command doesn't fail, and confirm that it starts browsersync (not sure how to detect the port).

@balintk any suggestions on how we might go about testing that the tasks and command line options?

[jameswilson]

For now. I'm going to commit and merge the test folder, we'll suffice with manual eyeball tests.