evalweb: Drop .parser from imports

evalweb/evalweb.py

 from flask import Blueprint, render_template, request
 from flask_wtf import FlaskForm  # type: ignore
 from wtforms import RadioField   # type: ignore
-from lib.parsing.parser import ParsingError
+from lib.parsing import ParsingError
 from evalweb.web_checker import WebChecker, Language, CompositeException
 from evalweb.examples import examples, convert_examples
 from typing import Optional

evalweb/examples.py

 from typing import Dict, Tuple
-from lib.parsing.parser import Parser
+from lib.parsing import Parser
 
 parser = Parser()
 examples: Dict[Tuple[str, str], Tuple[str, str]] = {}

evalweb/web_checker.py

 import lib.reg as reg
-from lib.parsing.parser import Parser, ParsingError
+from lib.parsing import Parser, ParsingError
 from lib.checker import transform, dfa_transform, nfa_transform, check_task, \
                         check_alphabets
 from typing import List, Optional