Add SequenceFile/WritableSequence tests
Added the Sum optimization
Merge branch 'develop' of github.com:twitter/scalding into feature/optimizedmatrix
More specific type for collecting addends
Choosing different join algorithms in Products based on SizeHints
Removed the additional special case for Sum
Added a simple difference/negation optimization
Added reducers option to the new join functions
Merge pull request #554 from tomtau/feature/optimizedmatrix

Feature/optimizedmatrix
Merge pull request #556 from vitalyg/develop

Added reducers option to the new join functions
Merge pull request #486 from daikeshi/develop

Add local scheme for SequenceFile and WritableSequenceFile to enable MemoryTap in Test