Add support for uniqueItems.
Fix inverted comparison.
Fix property path handling.

- avoid "undefined" when top level is an array.
- replace '.' in properties with '\.'.
Add value and schema to errors.
Add missing schema and value to type error.
Add more verbose handling.

- Use a common addError in checkObj.
- Print out schema and value if given.
Improve missing property error message.
More verbose property error messages.

Include property name to make error messages easier to quickly read.
Check that integers are numbers.

This typeof check ensures that falsey values such as null and undefined
are not considered integers.
Make unionErrors a union of errors (it wasn't before).
Ensure array values are invalid w/type 'object', fix concat usage.
Merge pull request #1 from digitalbazaar/master

pull from digitalbazaar branch