translation table. force to latin-1. see #17. @mruffalo : care to check on python3?
Fix nucleotide complementing for Python 3, for #17

Don't try to call .decode('latin-1') on a dict.
Fix doctests for Python 2 and 3

The pyfasta code uses text strings (str in Python 3, unicode in Python 2)
internally in most places, and it's difficult to directly check the __repr__
of these objects against known values in a way that works in both versions.
unicode.__repr__ has a 'u' prefix in Python 2, but this is not present in
str.__repr__ in Python 3.

To get around this, explicitly call print() on everything that we're
checking.