Feat: repr() uses class name and Travis-CI fixes

[alastairmccormack]

I regularly use AttrDict to quickly convert JSON objects into what looks like native objects.

When getting the repr, it's nicer to see the subclassed name rather than AttrDict.

E.g.

>>> class MySubClass(AttrDict):
>>>    pass

>>> msc = AttrDict({})
>>> print(msc)
'MySubClass({})'

[coveralls]

Coverage remained the same at 100.0% when pulling a7421d9 on use-sparingly:feature/repr_subclass_name into 9f67299 on bcj:master.

[coveralls]

Coverage remained the same at 100.0% when pulling f6b6fde on use-sparingly:feature/repr_subclass_name into 9f67299 on bcj:master.

[alastairmccormack]

To make the Travis CI build pass I've had to drop Py 3.2 and 2.6 tests. It seems that many libraries are dropping support which is causing pip install to fail on these versions.