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.
Merge pull request #9 from zerd/master

Add servlet filter and jersey client filter