docs(README): add testing section
docs(README): add testing section

nateabele/ui-date,mauricionr/ui-date,CommandLineDesign/ui-date,Sanjo/ui-date-multiselect,Recras/ui-date,CommandLineDesign/ui-date,joshorvis/ui-date,sterlingw/ui-date,tjwoon/ui-date,zhaokunfay/ui-date,alexanderchan/ui-date,alexanderchan/ui-date,drocbuster/AngularExamples,drocbuster/AngularExamples,joshorvis/ui-date,tjwoon/ui-date,zhaokunfay/ui-date,Recras/ui-date,sterlingw/ui-date,angular-ui/ui-date