Fix integer check

If we use "type": "integer", and property is boolean we got an error result (true).
Must be false, because boolean values (true/false) is not a integer.

UPD: Take into account the integer in string.
Merge pull request #19 from bayandin/patch-2

Fix integer check
added missing use statement for Validator-Class
Merge pull request #20 from rejinka/master

Missing use statetment added
stop validation on object of value Undefined
Merge pull request #22 from paranoiq/master

wrong handling of "required": false (closes #21)