Added the ability to use keywords for labels/properties.
Added basic documentation for the two helper methods.
Some values of maps returned by neo4j are now keywords to be consistent with the input.
From `clojurewerkz.support.http.statuses`, as we are only using `missing?` function, refer to it directly.
Merge pull request #36 from michaelklishin/labels-less-strict

We are now able to use keywords for labels