Fold %A into %O

Use the alternate form flag in conjunction with `%O` to print only
enumerable properties.  This resolves the conflict with the POSIX
specification and reduces the likelihood of future clashes (if we
were to use another conversion specifier instead).

Closes wdavidw/node-printf#9.
Bump version

ea216af is a backwards compatibility–breaking change, so the minor
version has to be bumped, according to SemVer.
Merge pull request #13 from AluisioASG/alternate-object-formatting

Convert %A into %#O