add fuzzy kmeans application
Merge pull request #123 from fegin/master

Naming conflict fixed
fix the comments
add spectral_clustering application
rm empty lines in the end of the spectral_clustering
Merge pull request #122 from MaggieQi/master

add fuzzy kmeans application
add distance measurement option for spectural clustering application
Merge pull request #124 from MaggieQi/master

add spectral_clustering application
Prettier string representations for most nodes.

The default debug string is useful for... debugging.

It's a little too much information for most purposes.  Change
the default representation to be a bit prettier.