Update javascript-stacktrace to tag 0.5.3.

Update javascript-stacktrace in the notifier to version 0.5.3.

This fixes an issue Chrome 27 being recognised as Firefox. Chrome 27 no longer has the 'arguments' property for exceptions (https://github.com/eriwen/javascript-stacktrace/commit/42f662127048c57b8c5ff87f4aa2ebb40d3a2d2b)