VERSION 0.9.1: bug fixes and experimental bridging support

This version fixes several bugs including an issue with networks that have
EtherType filtering disabled, a file permission issue that affected non-English
versions of Windows, a multicast propagation bug that caused multicasts to
be dropped more often than they should be, and an issue with IP auto-configuration.

It also introduces experimental support for bridging between physical and virtual
networks, a much-requested and powerful ability that's been planned from the start.
ZeroTier One can now replace the functionality of ordinary VPNs, link multiple
offices into a single LAN, and connect virtual machine backplanes in the cloud to
physical networks at home, among other things.

Bridging support isn't "officially" out yet, since the web UI part is still
in development. But when that is done, an official announcement will be
made on the blog and users can try it out. So far bridging has only
been tested under Linux with the Linux kernel's native bridging driver.
YMMV on other platforms. Try it out and let us know by filing bugs at GitHub
or e-mailing them to "contact@zerotier.com".