Fix magento root directory detection false positive
Fix magento root directory detection false positive

Search for index.php in addition to app/, skin/ and lib/ - this
should prevent MageRun from identifying module directories as
the Magento root by mistake

Fixes #229

twslade/n98-magerun,tkn98/n98-magerun,therouv/n98-magerun,TriplesenseReply/n98-magerun,chadbean/n98-magerun,therouv/n98-magerun,adam-paterson/n98-magerun,twslade/n98-magerun,sgrund/n98-magerun,EmPeWe/n98-magerun,othermedia/n98-magerun,oasisfleeting/n98-magerun,kojiromike/n98-magerun,oasisfleeting/n98-magerun,EmPeWe/n98-magerun,p-makowski/n98-magerun,tkn98/n98-magerun,bluec/n98-magerun,bluec/n98-magerun,iMi-digital/imi-conrun,AydinHassan/n98-magerun,othermedia/n98-magerun,iMi-digital/imi-conrun,TriplesenseReply/n98-magerun,davidalger/n98-magerun,p-makowski/n98-magerun,pocallaghan/n98-magerun,adam-paterson/n98-magerun,TriplesenseReply/n98-magerun,davidalger/n98-magerun,kojiromike/n98-magerun,iMi-digital/imi-conrun,adam-paterson/n98-magerun,pocallaghan/n98-magerun,EmPeWe/n98-magerun,oasisfleeting/n98-magerun,davidalger/n98-magerun,sgrund/n98-magerun,kojiromike/n98-magerun,pocallaghan/n98-magerun,bluec/n98-magerun,p-makowski/n98-magerun,chadbean/n98-magerun,twslade/n98-magerun,chadbean/n98-magerun,sgrund/n98-magerun,tkn98/n98-magerun