cidr 0.2.0

Added

• Implement IntoIterator for IpCidr structs
• Support (and require) various default traits
• InetPair: pair of two addresses in the same network
• Implement "trait" functions directly on data types and only forward in trait impl (#6); this makes it easier to use datastructs without traits in scope.

Changed

• Made bitstring dependency optional. Use cidr = { version = "0.2.0", features = [ "bitstring" ] } to enable it.
• Removed serde from default features. Use cidr = { version = "0.2.0", features = [ "serde" ] } to enable it.
• Added std feature; enabled by default. Also mandatory for now as std::net isn't available in core.
• Seal trait implementations
• Renamed Inet::next to Inet::increment
• Iterators (on IpCidr structs) now return Inet items instead of flat addresses. Use .addresses() on the iterator type to only iterate over the addresses.