Add call to GoogleGenomics::authenticate
Update AllModalitiesDemo.md

Missed a spot for commit https://github.com/googlegenomics/codelabs/commit/0383d60be98771c2bbfe4b9705878400b535a045
Update AllModalitiesDemo.Rmd

Missed a spot for commit https://github.com/googlegenomics/codelabs/commit/0383d60be98771c2bbfe4b9705878400b535a045
Add instructions for contributions.
Merge branch 'master' of github.com:googlegenomics/codelabs
Merge branch 'master' into qc-codelab