Merge remote-tracking branch 'upstream/master'

Author: stepds

README.md

@@ -11,4 +11,13 @@ If you've created a web page, video, sideshow, or any other kind of media you th
 3. Commit your changes. 
 4. Submit a pull request.
 
-We've created a [sample pull request](https://github.com/DataScienceSpecialization/DataScienceSpecialization.github.io/pull/1) to show you what we would like to see in a pull request. If we think your creation is well made, informative, and adds something new to this repository of content then we'll merge your request and add you to our list of contributors. If you happen to notice any inaccuracies or idiosyncrasies on this site or in this site's content, please let us know by opening an issue.
+We've created a [sample pull request](https://github.com/DataScienceSpecialization/DataScienceSpecialization.github.io/pull/1) to show you what we would like to see in a pull request. If we think your creation is well made, informative, and adds something new to this repository of content then we'll merge your request and add you to our list of contributors. If you happen to notice any inaccuracies or idiosyncrasies on this site or in this site's content, please let us know by opening an issue.
+
+Before sending a pull request to this site you should ask yourself:
+
+1. Am I the creator of the content I'm submitting?
+2. Does my contribution teach?
+3. Does the content of my contribution clearly address topics in the Data Science Specialization?
+4. Could my contribution be seamlessly integrated into the canonical course materials?
+
+If the answer to any of these questions in no then you probably shouldn't send a pull request. If you're on the fence about #3 or #4, err on the side of sending a pull request! 

about.md

@@ -16,5 +16,5 @@ The [Data Science Specialization](https://www.coursera.org/specialization/jhudat
 
 ### Community Contributors:
 
-- Kevin Markham
+- [Kevin Markham](http://www.dataschool.io/)
 - Derek Franks

other.md

@@ -4,3 +4,6 @@ title: Other Resources
 permalink: /other/
 ---
 
+## Troubleshooting
+
+- [Installing xlsx and XML packages on Debian Wheezy](http://allanino.me/blog/programming/installing-some-r-packages/)

pml.md

@@ -4,3 +4,6 @@ title: Practical Machine Learning
 permalink: /pml/
 ---
 
+## Model Evaluation
+
+- [Simple Guide to Confusion Matrix Terminology (sensitivity, specificity, etc.)](http://www.dataschool.io/simple-guide-to-confusion-matrix-terminology/)

toolbox.md

@@ -8,4 +8,7 @@ permalink: /toolbox/
 
 ## Git/GitHub
 
-- [Git & GitHub Video Playlist](https://www.youtube.com/playlist?list=PL5-da3qGB5IBLMp7LtN8Nc3Efd4hJq0kD)
+- [Git & GitHub Video Playlist](https://www.youtube.com/playlist?list=PL5-da3qGB5IBLMp7LtN8Nc3Efd4hJq0kD) (also available for [download](https://drive.google.com/folderview?id=0BxRfg0msVmAoRlZFQjJ3T3VTOUE&usp=sharing) as mp4 files)
+- [A Beginner's Quick Reference Guide for Git Commands](http://www.dataschool.io/git-quick-reference-for-beginners/)
+- [Understanding the Relationship Between Git and GitHub](http://www.dataschool.io/github-is-just-dropbox-for-git/)
+- [Simple Guide to GitHub Forks](http://www.dataschool.io/simple-guide-to-forks-in-github-and-git/)