fix: use 'var' instead of ES6 'const'
docs: add missing 'return'
fix: typo
feat: dependencies
feat: add new options object

Gulp-lab now supports new options Object and options String. Options
Array is no longer supported! Options Object contains “emitLabError”
property by default set on false. If “emitLabError” is true, Gulp-lab
emits an Error on tests fails.
docs: new API
feat: add more tests