Im not a Ruby developer but It seems it's a server error, if just the template was not found you have 404 error but here is 500 error, so maybe checking how SMT works and if is working fine with client side templating system will give you much ideas.
Mohamed Cherif BOUCHELAGHEM
Update:
Do you have templates files?? As I understand you dont have templates files in the gist, just templates ids, put the id of template #app-template or #toolbar-template can.view('app-template',{})
Mohamed Cherif BOUCHELAGHEM