JAVA-1529: JSON Parser now does not allow unmatched trailing quotes on field names

1. JSONTest.java file to include 2 tests 
           JSON.parse("{ a\": 1 }");
           JSON.parse("{ a: { b\":1 } }");
Both of the above test cases should throw JSONParseException because of unmatched quote.

2. Added a snippet of code in file JSONCallback.java in the objectDone() method to fix the given issue.