* Allow returning of object references
`TYPE` is now also on `IntoZval` which means `FromZval` does not need to
be implemented on return types
* Clippy lints
* Replace `ZendObjectOverride` derive macro with `#[php_class]`
* Updated guide with `#[php_class]` macro
* Panic rather than return error when implementing interface
It's gonna panic either way so might as well make it easier for the
builder
* Remove `libc` dependency
* Started work on guide, added types
* Rewrite argument parser to allow referencs
Primarly so that `&str` is a valid parameter type.
* Remove generic `Into<String>` conversion to exception
* Worked on guide, added macros
* Build guide when building docs
* Allow manual trigger of docs build
* `cargo fmt`
