fix(crawler): Try SoupParser for ValueError exceptions.

Couldn't reproduce in tests.
Exceptions:

All strings must be XML compatible: Unicode or ASCII, no NULL bytes or control characters
Unicode strings with encoding declaration are not supported. Please use bytes input or XML fragments without declaration.
Example URls:

http://www.teenvogue.com/fashion/2014-10/chanel-party
http://www.melconway.com/Home/Committees_Paper.html
Merge pull request #49 from cronycle/fix/ValueError-exceptions

fix(crawler): Try SoupParser for ValueError exceptions.