v0.8.2

Added:

• Enable generating a schema from any serializable value using schema_for_value!(...) macro or SchemaGenerator::root_schema_for_value()/SchemaGenerator::into_root_schema_for_value() methods (#75)
• #[derive(JsonSchema_repr)] can be used on C-like enums for generating a serde_repr-compatible schema (#76)
• Implement JsonSchema for url::Url (#63)