depend on edn-java 0.4.0 (release)
upgrade junit dependency from 4.10 to 4.11
deploy builds to oss.sonatype.org by default
replace conditionals with polymorphism

What exactly happens when newParserConfigBuilder(NilPolicy) is run
depends only on NilPolicy, therefore make it a method of NilPolicy.

Also, remove some (probably premature) "optimization" that cached
instance of the Guava*Factory classes in static finals so as to be
able to share instances. On further thought, I don't expect the
creation of parser configurations to occur so often that it would
benefit.

This simplifies the implementation.