Test case showing persistent connection problem.
See issue tntim96/JSCover/#91
Drop Proxy-Connection, Connection and Accept-Encoding headers when
proxying GET requests.
Header filtering from common method.
Persistent connection prevention fixed for POST requests.
Additional unit tests.  All tests now pass and coverage requirements
are met.
Add GPL header to PersistentStaticHttpServer.
Fix some logging statements. Minor tidying.
Update history and contributors