support bool and null values in createWith model attributes
ignore null values in createWith

From the Neo4j docs: NULL is not a valid property value. NULLs can
instead be modeled by the absence of a key. So we’ll just ignore the
keys when they occur.
Fix #16

In the case of fetching nested relations, we will get an array
with the first key being the model we need, and the other being the
related model which is the behavior of returning related results so
we'll just take the first model out of the results which is the
designated model.
Merge branch 'master' into develop
type-cast id(n) into int values in where clauses

closes #27