Release v1.3.0-rc4

Release v1.3.0-rc4 which contains the fix for
BGP netlink error.

Signed-off-by: Ryu Ishimoto <ryu@midokura.com>
Merge pull request #91 from midokura/ryu/relelase_v1.3.0-rc4

Prepare for v1.3.0-rc4 release