A 17-year-old Janesville boy is in custody after a convenience store robbery.  Janesville police say officers were dispatched to Lion’s Quick Mart on East Racine Street just after 8:30 a.m. Wednesday for a report of a robbery.  A male suspect with a gun had entered the business and demanded merchandise.  Police had circulated a photo of the suspect in seeking the publics help.  A news release indicates a tip led them to a residence in the 600 block of South Franklin Street about 7:00 p.m. Wednesday, where they arrested the teen on a charge of Armed Robbery.  The release also states a subsequent search of the residence yielded evidence of the robbery and a firearm.