Implemented binary IO and tests for AvroInt, AvroLong, AvroBoolean, AvroBytes, AvroNull, and AvroString.
Merge branch 'master' into io

Conflicts:
	build.sbt
	src/main/scala/com/gensler/scalavro/types/AvroType.scala
Added a retry limit for updating the complex type cache.
Added a retry limit for updating the complex type cache.
Experimental work toward integrating unboxed union type definitions.
Merge branch 'unboxed-unions' into io
Implemented IO for floating point primitives (AvroDouble, AvroFloat).
Updated the README to reflect completion of primitive type IO.
Implemented write binary for AvroRecords, which defers to the Java implementation from Apache.
Implemented binary read for AvroRecord; the implementation is still deficient from several perspectives: the Apache schema resolution mechanisms are not yet exposed through the API, generated schemas may be insufficient for the GenericDatumReader/Writer in the case of aggregate complex types.
Added missing comments to ReflectionHelpers.scala.
Moved existing classes into a sub-project called 'core', created a new (empty) sub-project called 'io', created SBT specific boilerplate necessary for multi-project build.
Cut out all read/write routines from scalavro-core, moved to new sub-project scalavro-io.  Cut out c.g.scalavro.util package into its own new sub-project scalavro-util.
Separated IO tests from the core specs to jive with the recent multi-project build trifurcation.