Add dev dependencies for automated testing
Add dev dependencies for automated testing

This makes it clear and explicit which node modules we need to run
tests.  Anyone installing Shaka Player via npm can get the deps
automatically.

Change-Id: I77456d3351775444a2bc669dd0129ce4afc0d1a6

ustudio/shaka-player,cmgrecu/shaka-player,baconz/shaka-player,ustudio/shaka-player,brightcove/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,indiereign/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,vimond/shaka-player,russitto/shaka-player,indiereign/shaka-player,cmgrecu/shaka-player,cmgrecu/shaka-player,TheModMaker/shaka-player,TobbeEdgeware/shaka-player,TheModMaker/shaka-player,russitto/shaka-player,indiereign/shaka-player,baconz/shaka-player,TheModMaker/shaka-player,Ross-cz/shaka-player,Ross-cz/shaka-player,baconz/shaka-player,vimond/shaka-player,TobbeEdgeware/shaka-player,russitto/shaka-player,TobbeEdgeware/shaka-player,ustudio/shaka-player,brightcove/shaka-player,vimond/shaka-player,shaka-project/shaka-player,ustudio/shaka-player,brightcove/shaka-player,TheModMaker/shaka-player,tvoli/shaka-player,tvoli/shaka-player,tvoli/shaka-player,Ross-cz/shaka-player