added parsing tests for simple values

Some tests for invalid values failed.

    PASS   : TestParser::parseInvalidSimpleValue(true)
    FAIL!  : TestParser::parseInvalidSimpleValue(string) '!ok' returned FALSE. ()
    Loc: [/home/taurus/develop/qjson/tests/parser/testparser.cpp(122)]
    FAIL!  : TestParser::parseInvalidSimpleValue(string2) '!ok' returned FALSE. ()
    Loc: [/home/taurus/develop/qjson/tests/parser/testparser.cpp(122)]
    FAIL!  : TestParser::parseInvalidSimpleValue(unicode string) '!ok' returned FALSE. ()
    Loc: [/home/taurus/develop/qjson/tests/parser/testparser.cpp(122)]