No slimes spawn in the new swampland biome witch then means you can not get slimes I am not sure if this has been fixed or not but it was broke in 13w38a this was in a new generated world.
Linked issues
duplicates 1
Comments 3
Also note, according to the Minecraft Wiki, slime spawn rates in swamps are affected by the current phase of the moon, with the most slimes during full moons and no slimes at all during new moons. For more details, check the wiki: http://minecraft.gamepedia.com/Slime
Unable to reproduce. Also note that you can sometimes find slimes in caves.