java 8, memory tuning

This release features changes to eureka-client library that reduce the memory footprint during JSON deserialization. The code was reworked to use Jackson stream-based parsing rather than an intermediate 'TreeNode' model, and revised string handling and caching cut heap allocations significantly.

The project has also been updated to use Java 8; the new code makes use of various features such as lambdas and Map's 'computeIfAbsent'.