19 - Test Checker#check(..) with a mocked IExtractor
20 - Progress reporting during detection and introduction to
Thread/Runnable and preliminary concurrency
21 - Better unknown content type and dead link reporting (Repetition of
different Collection characteristics (Set,List,TreeSet) and order)
22 - Report link currently extracted (logging repetition)
23 - Use system property to allow external configuration of threshold
level
24 - Java 1.7 multi catch statement (to handle https exceptions when no
network connection)
25a - Use pool of threads to concurrently recurse into link checking to
max out system resource (Synchronization done via
AtomicInteger)(MockedCheckerTest broken)