Update appveyor: no more bower, use yarn.
Update appveyor: no more bower, use yarn.

QuantumInformation/ember-cli-typescript,emberwatch/ember-cli-typescript,QuantumInformation/ember-cli-typescript,QuantumInformation/ember-cli-typescript,QuantumInformation/ember-cli-typescript,emberwatch/ember-cli-typescript,emberwatch/ember-cli-typescript,emberwatch/ember-cli-typescript