embedURL and thubmURL are now methods on prototype object

This allows them to update the youtubeID (say a typo) and recalculate the
string with each invocation so it will reflect the change.

Updated the solution file and the instruction file to reflect the change.
Use Array.prototype.map method over iteration

Inlcuded a link to the mdn for more reference. I'd like to
make students more aware of these methods.
Updated starting point for challenge 2 to reflect iterator methods

Also introduced forEach in the videos loop in the document.ready call.
updaetd starting point for challenge 2 to include new methods
Merge pull request #2 from ksolo/for-loop-to-map

Use Array.prototype.map method over iteration
Merge pull request #1 from ksolo/calculated-fields-become-methods

embedURL and thubmURL are now methods on prototype object