Fix exception class typo
Thank Josha for small fix in Tests/common_BioSQL.py

Raised during https://github.com/biopython/biopython/pull/234
Add comment about cStringIO vs StringIO problem
Tweak test_SeqIO_QualityIO.py to allow cStringIO

Using cStringIO.StringIO("") gives a read only handle.
Using cStringIO.StringIO() gives a writeable handle.

Using StringIO.StringIO("") or StringIO.StringIO() gives
a writeable handle.
Standardise StringIO imports in tests
Implment StringIO import via Bio._py3k module

The goal here is to facilitate writing code which can be
run on both Python 2 and Python 3 without alteration via
2to3 (and fixing these imports currently needs 2to3).
Import StringIO via _py3k module in tests
Option to tag files as Python 2 only, or dual syntax Python 2 and 3
Update StringIO/BytesIO imports in run_tests.py

This is enough to run this file unmodified on both Python 2.6+
and Python 3.3
These files work unmodified on Python 3

Focussed on Tests/test_*.py which are quick to test, and
files which were particularly slow to convert via 2to3.
Tag the BioSQL test files needing 2to3 conversion