Features from optional dependencies

handlebars implicit feature

Enables handlebars ^2.0

handlebars:

Handlebars templating implemented in Rust

serde implicit feature

Enables serde

serde:

A generic serialization/deserialization framework

serde_derive implicit feature

Enables serde_derive

serde_derive:

Macros 1.1 implementation of #[derive(Serialize, Deserialize)]