v0.2

• According to rtnetlink(7), ifi_change in struct ifinfomsg "is reserved
  for future use and should be always set to 0xFFFFFFFF", so did that.
• Added a new typeclass, Dump, that encodes request-reply pairs that can be
  used with dump.
• Added Integral and IsString instances for appropriate newtypes.
• Added general LinkType for creating links, instead of creating a new type
  for each kind of link.
• Added several new types to Address.hs, including ones for interface scope,
  precedence, labels, lifetimes, and IPv6 features.
• Added several new types to Link.hs, including ones for bridge slaves, link
  groups, and link stats.
• Added support for creating and managing vlan interfaces.
• Removed redundancies in Create, Destroy, Change, and Dump
  typeclasses, as well as header classes. This should drastically improve the
  DRYness of adding features.
• Fixed a bug that prevented nested struct nlattrs from being parsed.
• Made many minor interface improvements.