v0.8.3

To resolve #134, upgrade json4s dependency to v3.2.11.

p.s. in json4s v3.2.11_2.10, the method signature of JsonMethods.render was changed
from

def render(value: JValue): T

to

def render(value: JValue)(implicit formats: Formats = DefaultFormats): T

which caused a binary incompatibility.