v0.4.7

Fixes

• Disable libc default features so that CI continues to work on rust 1.13
• Fix panic on negative inputs to timestamp_millis (@cmars #292)
• Make LocalResult Copy/Eq/Hash

Features

• Add std::convert::From conversions between the different timezone formats (@mqudsi #271)
• Add timestamp_nanos methods (@jean-airoldie #308)
• Documentation improvements