Use foldLeft in Seq GCD.
fix a few kleene demo bugs
Faster derivative/integral for PolySparse.
Move gaussian-related methods to Generator.
Add vectorspace related type classes for Dist.
Add Dist#gaussian function.
Merge pull request #154 from tixxit/topic/dist-vectorspaces

Add vector space instances for Dist and add gaussian methods to Generator.
Allow full range for nextInt and nextLong.
add missing option instances
add metric space syntax
add CMonoid, a commutative monoid
Add CRing[A].
Merge pull request #155 from non/topic/commutativity

Topic/commutativity
first pass at a spire guide
fix some typos in GUIDE.md
Test deps for scala{test,check} for spire-macros.
small guide update
Added Polynomial.interpolate and cleaned up return types.
Add ZModule and sumn methods to Monoid/Group.
Use #sumn if possible, instead of reimplementing it.