Improve integration test by only settings up ZipkinCollectorServer once for both tests.
Small refactorings

Extracting some methods.
Checking for isDebugEnabled is not necessary when the logging statement is inexpensive.
Add module for jersey-client integration

Added a small filter for jersey-client that you can install to create a span for requests and forward headers.
Also added a servlet filter that you can add to web.xml or similar to get the span from incoming requests or create a new one.
Add .iml and .idea to gitignore.
Add unit tests for servlet trace filter.