Replace embeded videos redirect

All video resources redirect to the dedicated YouTube GitHubGuides channel for simplifying access.

Non-GitHubGuides channel videos that may need uploading to YouTube include these:

[Git-SCM Official Site Videos](http://git-scm.com/videos)
[Matthew's Git Videos](https://pinboard.in/u:matthew.mccullough/t:git+video)
[Git Configuration](http://githubtraining.s3.amazonaws.com/github-training-screencast-configsetup.mov)
[Adding and Committing](http://githubtraining.s3.amazonaws.com/github-training-screencast-basicsaddandcommit.mov)
[Logging](http://githubtraining.s3.amazonaws.com/github-training-screencast-logging.mov)
[Branching](http://githubtraining.s3.amazonaws.com/github-training-screencast-branching.mov)
[Conflict Resolution Editing](http://githubtraining.s3.amazonaws.com/github-training-screencast-conflictresolveeditor.mov)
[Fork and Pull Request](http://githubtraining.s3.amazonaws.com/github-training-screencast-forkandpullrequest.mov)
[Squash Merge](http://githubtraining.s3.amazonaws.com/github-training-screencast-squashmerge.mov)
[Bisect](http://githubtraining.s3.amazonaws.com/github-training-screencast-bisect.mov)
[Smart Git Basics](http://githubtraining.s3.amazonaws.com/github-training-screencast-smartgit.mov)