Released v7.1.1
* Check that the wheel cache directory is writable before we attempt to write
cached files to them.
* Move the pip version check until *after* any installs have been performed,
thus removing the extraenous warning when upgrading pip.
* Added debug logging when using a cached wheel.
* Respect platlib by default on platforms that have it separated from purlib.
* Upgrade packaging to 15.3.
* Normalize post-release spellings for rev/r prefixes.
* Upgrade distlib to 0.2.1.
* Updated launchers to decode shebangs using UTF-8. This allows non-ASCII
pathnames to be correctly handled.
* Ensured that the executable written to shebangs is normcased.
* Changed ScriptMaker to work better under Jython.
* Upgrade ipaddress to 1.0.13.