object with additionalProperties=false should not admit additional fields

Previosuly, a schema having an empty object (one with no "properties")
would admit additional fields even when additionalProperties was set to
false.

Closes #5, originally from jluxenberg@52f90016b3151cffdb436929598c5f93c6ba6e29
Fix dependencies
Version 1.0.4
Dev is 1.0.5-SNAPSHOT