Activate gd and mbstring on Heroku
Activate gd and mbstring on Heroku

Seems like opt-in. Hope it works

Ref:
- https://devcenter.heroku.com/articles/php-support#php-5-5-and-5-6

walutisme/grav-test,walutisme/grav-test,akhyarrh/grav-test,akhyarrh/grav-test,walutisme/grav-test,walutisme/grav-test,akhyarrh/grav-test,akhyarrh/grav-test