Add vs-select-group solution errors

new components

• vs-select-group

new features

• select: ahora puedes tener un grupo de opciones

issues solved

Error raised on clicking vs-select #256
Add ability to add grouped options in a select field. #233
Vue router and dropdown: Error in beforeDestroy hook: "RangeError: Maximum call stack size exceeded" #257

merge pull requests

Fixes #257 dropdown component #258 @rendoh