add a responsive option for ima, combined 5commits:
Configuration. Query whether option isResponsive is set or not and replace
fixed values by relative values for this setting,

add site holder div and responsive video/iframe container,

add a demo css with responsive stylings for video and ad overlays,

copy configuration file,

copy config file from simple example, add isResponsive option
Merge branch 'master' of https://github.com/webdesignberlin/videojs-ima