mysql-connector fix for issue #370

According to the [release notes](http://dev.mysql.com/doc/relnotes/connector-python/en/news-2-0-0.html) of the mysql-connector for Python,  bytearray objects are now returned by raw cursors when fetching text data. This is partly due to them moving to a unified codebase for Python 2 and 3 and is acknowledged as a backwards incompatible change.

To fix this issue, a new Adaptor class has been added to BioSQL to handle mysql-connector connection objects. This Adaptor object will now scrub the returned data, converting bytearray objects and byte strings into string objects correct for the python version. This change should not affect users of older mysql-connector versions since the scrubbing function will return the data unaltered.

Other database connections will continue to use the default Adaptor object.