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Merge pull request #121 from sahat/patch-1

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fix: Pass node-specific command line params to the subprocess

This commit makes the karma task pass Node-specific parameters used to start
the Node process to its background subprocess. This is required e.g. to be able
to use the --harmony flag.

Similar pull request for Grunt itself (already merged):
https://github.com/gruntjs/grunt/pull/877