Update en.yml

Revised to remove Google Doc for getting involved. Discussed with Tim and Christina.
Update en.yml

Added a temporary note with regard to image uploads:  "If you get an error message, please try again with fewer or smaller files."
Merge pull request #133 from avicaplan/patch-1

Remove Google Doc link for getting involved and add error explanation for image errors.

Still needs pt.yml and fr.yml localization.