Add yarn install to Dockerfile.dev in an attempt to fix Travis CI builds.
Add yarn install to Dockerfile.dev in an attempt to fix Travis CI builds.

fle-internal/content-curation,jayoshih/content-curation,jayoshih/content-curation,DXCanas/content-curation,fle-internal/content-curation,jayoshih/content-curation,DXCanas/content-curation,fle-internal/content-curation,DXCanas/content-curation,jayoshih/content-curation,fle-internal/content-curation,DXCanas/content-curation