Maintenance release

This release brings bug fixes, a missing feature needed for CNI integration and internal improvements.

New features:

• FLANNEL_NETWORK will be printed to subnet.env with the CIDR value of the whole network. Makes CNI integration possible.
• Add logos to docs

Bug fixes:

• Don't propagate own lease notifications to backends.
• Eliminate race in http request cancellations in the tests.
• Fix for kernels that report "special" ARP entries with nil IP that caused VXLAN to not work
• mk-docker-opts.sh -- -m options was not processed

Internal improvements:

• Switch to new etcd client lib
• Switch to using go-iptables lib
• Switch to using flagutils lib