added parts support
NBC - Support urls with 'classic-tv' and/or without a show name in the url.
added comment for parts
CollegeHumor - Fallback to low quality video if high quality is not available
RTL XL - Use framework function for calculating duration; make indirect.
CollegeHumor - Check if json key 'mp4' exists
Extreme - Skip over missing summaries
Merge pull request #686 from shopgirl284/mtvaddparts

Add ability for parts to be sent with URL
MTV - Assign normalized url to variable. Check for #parts= first.
The Colbert Report - Catch and log http error(s); xpath updates.
Vimeo - That's not how you spell 'json' :p
Vimeo - Extra check for available json_obj var