“The Colbert Report” dedicated about a third of last night’s episode to a lively discussion about Prop 19 in California – and it was chalk full of gems. After rallying his audibly excited audience with an overview of where the measure stands (“If Prop 19 were a human, it would be the most popular candidate in California”), host Stephen Colbert turned to two guests – Joseph Califano, of the Center on Addiction and Substance Abuse, and former New Mexico Governor Gary Johnson – to argue for and against…