Adding Display Id parameter to Storage Video URLs

Entry point constants to uppercase
Merge pull request #15 from alex-deaconu/bug/video-source

Add Display ID Parameter to Storage Video URLs
Fixing issue with obtaining the extension for Videos

Only adding display Id for displays
Added failsafe for extension checking
App Engine version bump
Merge pull request #16 from alex-deaconu/master

Fixing issue with obtaining the extension for Videos
[bugfix] Changed the Cache file url encoding
Merge pull request #19 from alex-deaconu/master

[bugfix] Changed the Cache file url encoding
Production variables