Adds a weighted PageRank example using Matrix API

Using the Matrix API only, runs a weighted or
unweighted PageRank algorithm. This functions in
a similar way to the existing weighted PageRank
example. See the inline Scaladoc for more details.
Merge pull request #256 from joshdevins/matrix-api-weighted-pagerank

Adds a weighted PageRank example using Matrix API
Add a partition method to RichPipe.
Rough outline of a partition job test.
Fix partition test.
Change partition to take a generic function from A->R, not just a predicate function.
Field -> Fields
Add arity match assert and discard tmp fields.
Fix PartitionJob test by specifying the order of the output fields.
Merge pull request #246 from arkajit/partition

Create a Partition method for RichPipe.
Update some versions
Merge pull request #264 from johnynek/feature/version-bump

Update some versions