Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features.

bigdecimal implicit feature

Enables serde of bigdecimal ^0.3.0

email_address implicit feature

With serde and default (serde_support)

num implicit feature

With serde and default (std)

peginator implicit feature

Enables peginator ^0.3.0

semver implicit feature

With serde and default (std)

serde_json implicit feature

With default (std)

url implicit feature

With serde

uuid implicit feature

With serde and default (std)