Merge pull request #19 from bmcollings/patch-1

Update 05-clustering.md - fix link for spectral clustering

_episodes/05-clustering.md

@@ -185,7 +185,7 @@ plt.show()
 ## Spectral clustering
 
 Spectral clustering is a technique that attempts to overcome the linear boundary problem of k-means clustering.
-It works by treating clustering as a graph partitioning problem and looks for nodes in a graph with a small distance between them. See [this](http://www.cvl.isy.liu.se:82/education/graduate/spectral-clustering/SC_course_part1.pdf) introduction to spectral clustering if you are interested in more details about how spectral clustering works.
+It works by treating clustering as a graph partitioning problem and looks for nodes in a graph with a small distance between them. See [this](https://www.cvl.isy.liu.se/education/graduate/spectral-clustering/SC_course_part1.pdf) introduction to spectral clustering if you are interested in more details about how spectral clustering works.
 
 Here is an example of spectral clustering on two concentric circles: