Some of these environment variables are necessary codecov to
detect that it is on travis/appveyor and thus doesn't need
an upload token.

Stop patching write_pkg_info

Fix unicode maintainer

Add support for maintainer in PKG-INFO

Don't claim to provide the extra ''

Per PEP 345, metadata Version 1.2 should support the Author,
Maintainer, Author-Email and Maintainer-Email fields.