Upgrade Polymer CLI 1.6 -> 1.8
Upgrade Polymer CLI 1.6 -> 1.8

Hopefully fixes promisify issues with Node 10 on Travis

https://github.com/Polymer/tools/commit/29a85f97d066da538cb26b85278181a7dfb85b80

Signed-off-by: Patrik Kullman <8612fec4a6bb0a11ae3ca5e27ebb050b4a73b7ea@neovici.se>

Neovici/cosmoz-behaviors,Neovici/cosmoz-behaviors