Use semigroup in StateWithError
Merge pull request #255 from twitter/fix-state-with-error

Use semigroup in StateWithError
Make SketchMap1 into SketchMap
Update references to be to SketchMap not SketchMap1
Merge pull request #256 from twitter/jco/rename_sketchmap

Make SketchMap1 the only SketchMap implementation
Bump versions
Merge branch 'release/0.4.0' into develop
Implement StreamSummary data structure for finding frequent/top-k items
Some changes to StreamSummary as suggested by Oscar in pullreq comments
Rename StreamSummary to less generic SpaceSaver
Add Predecessible and methods to Interval
Simplify the lower/upper testing
Make prev use Integral
Address review comments
Add toLeftClosedRightOpen
only use Successible for toLeftClosedRightOpen
Make SketchMapMonoid params public
Merge pull request #265 from twitter/jco/264

Make SketchMapMonoid params public
Fix SketchMapMonoid zero
Merge pull request #269 from twitter/jco/fix_sketchmap_zero

Fix SketchMapMonoid zero