Version 0.4.0

• Make SketchMap1 the only SketchMap implementation: #256
• Use semigroup in StateWithError: #255
• Don't iterate through everything in unit monoid: #253
• Factor as much logic as possible into SketchmapMonoid1: #251
• Moving Trampoline flatMap implementation into trait: #249
• Integrate Caliper: #248
• Adds append method to MonoidAggregator and RingAggregator: #246
• Make the map monoid more performant for mutable maps: #245
• Make BFHash take on non negative values only: #243
• Fixed DecayedValue: #238
• Updated scaladoc to 0.3.0: #237
• Add Incrementable and tests: #234
• Updates sbt runner: #232
• Upgrade sbt, specs, add a build.properties, and bump travis's target: #231