Slightly better exception handling / fix issue #1

Hi JoKnopp,

When parsing the latest (Jan2013) rdf for dmoz, I ran into a few problems:
1. Sqlalchemy moved its exceptions into the .exc module in 0.7. That's fixed with the first commit, which should also solve issue #1.
2. This go around dmoz had an externalpage that contained a &#3; (ctrl-c), which sax considered invalid. I added a little error handling to log exceptions, skip the bad character, and keep parsing. I guess it's up to the end user to check and see if the data they get is good enough. Fixed in the second commit.
3. On my platform (Python 2.7.3 / Centos 5.8), sqlalchemy didn't like  
```python
encoding==utf-8
```
When configuring the db engine, saying that encoding should be of type str(), not type unicode(). That's probably because of the # -*- coding: UTF-8 -*- line at the top of the script. Anyway, that's also fixed in the second commit.

Hope these changes are of use!

-gnrhxni