Add JSON support:
 - rpc extensions to support both XML and JSON requests and responses
 - net support for a Eureka connection using JSON or XML
 - net support for marshalling and unmarshalling of the apps, app and instance structs
 - custom unmarshallers and intermediate wrapper structs to deal with nasty Eureka JSON
Cleaned up debug printf's by adding a couple new independent loggers.
Split out instance retrieval needed in ReregisterInstance() into new functions GetInstance() and readInstanceInto()
Small change to readAppInto() to match simpler form in readInstanceInto()
Removed noisy test output, fixed bad log format, and added error checking for port unmarshaling.
Merge pull request #6 from cquinn/master

Add JSON support: (credit: @cquinn)