Added JsonLong and JsonDouble cases for JsonNumber #116

Conflicts:
	src/main/scala/argonaut/DecodeJson.scala
	src/main/scala/argonaut/EncodeJson.scala
	src/main/scala/argonaut/Json.scala
	src/main/scala/argonaut/JsonParser.scala
	src/main/scala/argonaut/PrettyParams.scala
	src/test/scala/argonaut/CodecNumberSpecification.scala
	src/test/scala/argonaut/JsonSpecification.scala
	src/test/scala/argonaut/KnownResults.scala
	src/test/scala/argonaut/PrettyParamsSpecification.scala
	src/test/scala/argonaut/StringWrapSpecification.scala
Improved prettyprinting test