Install yarn explicitly
Install yarn explicitly

Previously Travis auto-installed yarn for us because we had a yarn.lock
file in the repository root -- now we no longer have this so we have to
manually set it up.

CatalystCode/bot-fmk-dashboard,CatalystCode/ibex-dashboard,CatalystCode/ibex-dashboard,CatalystCode/ibex-dashboard,garypretty/ibex-dashboard,CatalystCode/bot-fmk-dashboard,CatalystCode/ibex-dashboard,garypretty/ibex-dashboard,CatalystCode/bot-fmk-dashboard,garypretty/ibex-dashboard,CatalystCode/bot-fmk-dashboard,garypretty/ibex-dashboard