Parser incorrectly parses incomplete expression

Tested with python and the `jp` CLI, incomplete expressions should generate an error. Note the delta here:

```
$ jp --ast 'foo.'
SyntaxError: Expected identifier, lbracket, or lbrace
foo.
^
```

```
>>> import jmespath
jmespath.exceptions.ParseError: Expecting: ['quoted_identifier', 'unquoted_identifier', 'lbracket', 'lbrace'], got: eof: Parse error at column 8, token "" (EOF), for expression:
"foo.bar."
^
>>>
```

But in javascript:

```

> var jmespath = require('./jmespath');
undefined
> jmespath.compile('foo.');
{ type: 'Subexpression',
children: [ { type: 'Field', name: 'foo' }, undefined ] }
```

Javascript should be raising an error here.