Double faced cards are not handled correctly

[tooomm]

See e.g. #317

Unable to parse "Blood Crypt // Blood Crypt" (ECL): 'cmc'
Unable to parse "Hallowed Fountain // Hallowed Fountain" (ECL): 'cmc'
Unable to parse "Overgrown Tomb // Overgrown Tomb" (ECL): 'cmc'
Unable to parse "Steam Vents // Steam Vents" (ECL): 'cmc'
Unable to parse "Temple Garden // Temple Garden" (ECL): 'cmc'