Add support for sample with return
Implemented Donald Knuth's algorithm for Poisson random generation. Removed colt dependency.
Added support for FlowSkipStrategy and FlowStepStrategy on a Job.
hide the flowDef to improve encapsulation and facilitate creation of flows that do not have a flowDef such as riffle jobs
Merge pull request #497 from pcting/develop

FlowSkipStrategy and FlowStepStrategy
merge by hand
rename sampleWithReturn to sampleWithReplacement
Merge pull request #495 from itaibenari/develop

Add support for sample with return
Merge pull request #499 from tresata/feat-hide-flowdef

hide the flowDef to improve encapsulation and facilitate creation of flo...
Merge branch 'develop' of github.com:twitter/scalding into feature/optimizedmatrix