Upgrade to Scalaz 7.10 and all that entails

Farewell variance, we hardly knew ye.
Upgrade to SBT 0.13.6-M1
Rename MemoryConversion Numeric implicit def name to avoid shadowing
Add scalaz.Order for BytesQuantity
Upgrade rng to 1.3.0
Upgrade to scalaz-stream 0.5a
Invariant for the win.
Merge pull request #33 from ambiata/topic/scalaz-7.10-farewell-variance

Upgrade to Scalaz 7.10 and all that entails