Check for null websocket

Fix #744
Merge pull request #745 from bootstraponline/fix_null

Check for null websocket
Page source now retrieves source for all windows (not just the main window).  This means that the statusbar window, keyboard window, and any actionsheet/popover/alert windows will be logged.
Fixed broken unit tests related to having page_source return all windows (not just the main window).
Merge pull request #748 from kinghenry3/PageSourcePatch

Page source now retrieves source for all windows.
use cross-platform path.resolve in adb.js
touch/click is same as /click for mobile