Merge pull request #41 from echaozh/use-http-client

Use http-client instead of HTTP, for conn pooling
update dumpSessionHistory documentation
WDSession/WDConfig overhaul
more control over http requests to the webdriver server
closeSession in runSession on error too
refactored internals
minor change in handleJSONErr
Merge branch 'upstream-master'
Merge branch 'close-session'
Merge branch 'http-config'