Add new_assert implementations #57

• Add new_assert implementations #57

Add ser_as_str feature to serialize using serialize_str()

• Add ser_as_str feature to serialize using serialize_str() #52

Add no_std support on nightly

• Add no_std support on nightly #51

Allow to invoke some functions as const

• Allow to invoke some functions as const fn #43

Add IP netmask conversion and constructors

• Add IP netmask to prefix conversion functions and new with_netmask() constructors.

Fix JsonSchema implementation

• Manually implement JsonSchema for IpNet, Ipv4Net, Ipv6Net #41 because default derived JsonSchema does not correspond to Serde representation #40
• Migrate to edition 2018

Fix Error::description() deprecation warning

• Merge Fix Error::description() deprecation warning #28.

Implement Default on IpNet, Ipv4Net, and Ipv6Net

• Merge @imp's Default implementation. See #18. Ipv4Net and Ipv6Net now default to 0.0.0.0/0 and ::/0 respectively. IpNet defaults to the 0/0 Ipv4Net.

• Add #[allow(arithmetic_overflow)] for Ipv4AddrRange::count() and Ipv6AddrRange::count(). Since 1.43.0-nightly it gives a build error but this panic behavior is desired. In future it may be replaced with explicit use of panic!. See #21.

Implement conversion from IpAddr types to IpNet types

• Implement From<IpAddr>, From<Ipv4Addr>, and From<Ipv6Addr> for IpNet, Ipv4Net, and Ipv6Net respectively.

Implement Iterator methods, FusedIterator, and DoubleEndedIterator

• Implement FusedIterator for IpAddrRange, Ipv4AddrRange, Ipv6AddrRange, IpSubnets, Ipv4Subnets, and Ipv6Subnets.

• Implement DoubleEndedIterator for IpAddrRange, Ipv4AddrRange, Ipv6AddrRange.

• Implement custom count(), last(), max(), min(), nth(), and size_hint() for IpAddrRange, Ipv4AddrRange, Ipv6AddrRange.