0.6.0

CHANGES:

• add option for capturing packets directly on the interface (#30, @MagnusS)
• add option for unlocking a mutex when the interface is in listen mode (#30, @MagnusS)
• add package mirage-vnetif-stack to provide a preassembled ipv4 stack (#30, @MagnusS)
• add initial connect test for the vnetif-stack (#30, @MagnusS)
• clean up opam dependencies (#30, @MagnusS)
• drop mirage protocols and adapt to arp, ipaddr, tcpip interface
  changes (#33, @MisterDA)
• restore old behavior of mirage-vnetif to avoid breaking changes (f0b8341, @dinosaure)