Resolve promise if `grecaptcha` already exists
Resolve promise if `grecaptcha` already exists

Related to #24, recaptcha won’t load if it’s included in a secondary
view when using ng-route.

aaronroberson/angular-recaptcha,mrwogu/angular-recaptcha,TheSharpieOne/angular-recaptcha,aaronroberson/angular-recaptcha,mrwogu/angular-recaptcha,VividCortex/angular-recaptcha,romelgomez/angular-recaptcha,TheSharpieOne/angular-recaptcha,mmsqe/angular-recaptcha,romelgomez/angular-recaptcha