binary: Adopt functional style, add error handling

The Binary class and its __int__ method is replaced by the parse_binary
function as discussed in #79.
Instead of asking for a return value of 0 for invalid literals, the
tests now demand that a ValueError be raised.
Merge pull request #94 from sjakobi/functional-binary

binary: Adopt functional style, add error handling
bob: Use Python3 unicode literals, enhance whitespace tests
Merge pull request #95 from sjakobi/bob-unicode

bob: Use Python3 unicode literals, enhance whitespace tests