[build] Bumped sbt to 0.13.7
[rdf] Removed isURI from RDFOps.

Do not put such helper methods directly in typeclasses.
[rdf] Added operations over mutable graphs.
[jena] Support for MGraph.
[sesame] Support for mutable graphs.
[plantain-jvm] Fixed+improved model. Added mutable graph.
[plantain-js] Fixed model. Added mutable graphs.
[plantain-jvm] Use native types: Int, String.
[plantain-jvm] Add native Boolean.
[plantain-jvm] Add native Double.
[plantain-js] Fix compilation issue.
[io] Simplifications.

* no selector
* no Syntax
Merge branch 'topic/io-cleanup' into topic/mutable-graph
[tests] Bumped scalaz versions. Added scalacheck and SpecLite.
[mgraph] Added SpecLite tests and MGraph syntax. Fixed jena and sesame implementations.