Merge pull request #1 from dlogothetis/master

Fixes and refactoring in the graph tests
Update README.md
[FIX] couple of bugs after the early refactoring.
[MINOR] removed d default value from code
[FIX] runokapi had a bug
[FIX] formatting
[Debug] need to check the code of BPR
Added default log4j configuration
minor spelling fix
[FIX] forced initialization of vetexes
Merge branch 'develop'
[FIX] Sampling for ranking methods. The giraph has this thing about
optimizing the edge itarators. So you can not simply iterate and put
these into a collection. you need to do a copy...

[FIX] sampling now sends messages to all relevant...
[FIX] test adapted to the current sampling technique
Merge branch 'develop'
kmeans clustering implementation and simple tests
Merge branch 'master' of https://github.com/grafos-ml/okapi into kmeans_clustering
fixes bug with euclidean distance computation
added 2 more tests, using Stratosphere's KMeansDataGenerator
correct vertexID type in OutEdges
Fix in PrefixHashPartitionerFactory, compatibility with latest Giraph