Suggestion: Move data.locale in DateRangePicker.vue to computed

[passerby-cjl]

Thanks for your awesome project!
When using this project, the property 'locale' is computed once it is conveyed to DateRangePicker in the function data(). To meet the need of change locale, I suggest moving it to computed part.
The change should happen in file 'DateRangePicker.vue'. It will be a quick fix. Thx!