Implemented the Python attribute protocol

[apalala]

The behavior regarding attributes was unexpected.

Now these work:

hasattribute(element, 'aname')
getattribute(element, 'aname', [])

[coveralls]

Coverage decreased (-0.5%) to 36.73% when pulling c61743a on apalala:master into 06d60a8 on stchris:master.

[landscape-bot]

Repository health decreased by 0.81% when pulling c61743a on apalala:master into 06d60a8 on stchris:master.

• 1 new problem was found (including 0 errors and 1 code smell).
• No problems were fixed.

[stchris]

Looks good. Could you add some basic tests?

[landscape-bot]

Repository health decreased by 0.58% when pulling 338c880 on apalala:master into 06d60a8 on stchris:master.

• 1 new problem was found (including 0 errors and 1 code smell).
• No problems were fixed.

[coveralls]

Coverage decreased (-0.5%) to 36.73% when pulling 338c880 on apalala:master into 06d60a8 on stchris:master.

[apalala]

I added the test cases.

[stchris]

Awesome, thanks! Feel free to submit your name to the AUTHORS file if you'd like to be mentioned.