updated d3 version
added page visibility timeout for websocket messages
changed visibility timeout to 20 seconds
Merge branch 'master' into memleak.MLHR-670
Merge pull request #660 from andyperlitch/memleak.MLHR-670

Fixes memory issue when page not visible for extended period of time
providing text files instead of java files for testing
providing text files for testing
Merge branch 'master' of https://github.com/DataTorrent/Malhar into MLHR321DirectoryScanInputOperator