v1.0.0-beta.0

• Removed IntoValue and added ToValue because it now accepts a reference to self
• Custom types now have to be wrapped in a Pointer<T>
• Added ocaml::import! macro for calling OCaml functions from Rust
• Added ocaml::sig proc-macro for generating external and type signatures
• Added ocaml-build crate for generating OCaml code from ocaml::sig macros and linking dune
  projects
• Renamed Value::call to Value::call1 and rewrote Value::call to take a variable number of
  arguments
• Added support for automatic conversion between OCaml Result.t and Rust Result
• Renamed Value::float to Value::double and Value::float_val to Value::double_val
• Added Value::alloc_double_array, Value::double_field and Value::store_double_field
• Improved support for float arrays in ocaml-sys
• Custom values have a new default finalize implementation that will drop the inner Rust value