Upgrade to Java 8 and other changes.

Hi,
We are using Stubby4j, in a large scale and in multiple test suites for our project. We had to make few changes to accommodate our project needs in terms of monitoring, test stability and  maintainability.  These commits have following changes, 
1. Log request and response body. We need to make it optional through command line options.
2. Made Query params matching strict. Again we had to make it optional, if you feel so.
3. The post body comparison for request was converted to json comparison instead of text comparison. Yet we might have to make the comparison based on type of post body.
4. Added admin endpoint to give errors count, which we use it ensure the all the request went through which won't be directly asserted by test.
5. Added admin endpoint to give unused stub configuration. We were using custom scripts to parse log, finally we had to put this in place to keep the code base clean.
6. While parsing the configuration YAML file, when the request's post file or response file is missing, an error message is thrown, yet the configuration is loaded. This causes test to behave wrongly. Request with wrong post file gets response, and for missing response file we were sending blank response. We made such HttpLifeCycle's not to load as part of the StubDataManager. We are even considering blocking the server to start in such cases, in order to keep the code base stable. 
7. Had moved to use Java 8.