refactor quirks and allow bidirectional converters
cleanup unused ideas
add some docs
add test for two way converter
Merge branch 'master' into converters_v2

Conflicts:
	core/src/main/java/org/sql2o/PojoResultSetIterator.java
Merge pull request #70 from aaberg/converters_v2

Bidirectional Converters and Quirks