Add Cooperative Groups API integration

This works as follows:
- Users build their Cuda code via `CudaBuilder` as normal.
- If they want to use the cooperative groups API, then in
  their `build.rs`, just after building their PTX, they will:
  - Create a `cuda_builder::cg::CooperativeGroups` instance,
  - Add any needed opts for building the Cooperative Groups
    API bridge code (`-arch=sm_*` and so on),
  - Add their newly built PTX code to be linked with the CG API,
    which can include multiple PTX, cubin or fatbin files,
  - Call `.compile(..)`, which will spit out a fully linked `cubin`,
- In the user's main application code, instead of using `launch!` to
  schedule their GPU work, they will now use `launch_cooperative!`.

Chore: cuda_std 0.2.2

Chore: wrong nightly date in changelog