fixed broken license link
fixed broken license link

the current /license was 404. Updated it to https://github.com/slimphp/Slim/blob/master/LICENSE.

Thanks to derecho.elijah.cs.cmu.edu:8585/@top for finding the broken link.
fsciuti/Slim,dkarvounaris/Slim,greevex/Slim,silentworks/Slim,luizdeangeli/Slim,matheusgomes17/Slim,geggleto/Slim,cesarmarinhorj/Slim,jeremykendall/Slim,swantrace/Slim-1,tempbottle/Slim,lornajane/Slim,lmcro/Slim,lekoaf/Slim,kanellov/Slim,pedro2555/Slim,xMolchy/Slim,EhteshamMehmood/Slim,andresvidal/Slim,asaokamei/Slim,xiuchanghu/Slim,lcp0578/Slim,FraGoTe/Slim,jenalgit/Slim,bact197736/Slim,Vinniefern99/Slim,shameerc/Slim,huang53798584/Slim,beealone/Slim,kutanari/Slim,prashantquestionpro/Slim,szulilin/Slim,julianromera/Slim,chezzy/Slim,mmauri04/Slim,Alex2147483647/Slim,makelivedotnet/Slim,abfadel/Slim,zither/Slim,moufmouf/Slim,nslod/Slim,tanuck/Slim,taohaolong/Slim,joelgarciajr84/Slim,gencer/Slim,gabriel403/Slim,ColourboxDevelopment/Slim,anuradhaedirisuriya/Slim,1nv4d3r5/Slim