Don't use deprecated 'U' flag to read manifest

The universal newlines mode ('U' flag) is deprecated since Python
3.4. It only replaces "\r\n" with "\n", but it doesn't split lines at
"\r" (Mac newline). In practice, the flag was useless, the
sdist.read_manifest() method already uses line.strip() and so removes
newline characters.

readme: update links to documentation

Add a Gitter chat badge to README.rst

Update link to Resource Management API

Ensure package name isn't unicode in Python2 distutils