fix(config): Retry install with appveyor-retry.  
fix(config): Retry install with appveyor-retry.  

Workaround npm install issues
johnjbarton/karma,johnjbarton/karma,david-garcia-nete/karma,david-garcia-nete/karma,karma-runner/karma,david-garcia-nete/karma,maksimr/karma,johnjbarton/karma,karma-runner/karma,maksimr/karma,karma-runner/karma,karma-runner/karma,johnjbarton/karma,maksimr/karma