capnpc 0.8.7

Cap'n Proto code generation
Documentation
### v0.8.7
- Eliminate `use` statements in generated code to avoid naming conflicts.

### v0.8.6
- Improve error message for snake_case method names.
- Eliminate floating point literals in match statements.

### v0.8.5
- Implement enum defaults.
- Emit "UNIMPLEMENTED" warnings on struct and list defaults.

### v0.8.4
- Implement struct, list, and enum constants.

### v0.8.3
- Fix bug where schemas with non-trivial relative filesystem paths could fail to compile.

### v0.8.2
- Fix bug where `initn_*()` methods of generic unions failed to set the discriminant.

### v0.8.1
- Fix several formatting issues in generated code.
- Remove some unneccesary trait bounds in generated code.
- Add `import_path()` and `no_std_import()` options to `CompilerCommand`.

### v0.8.0
- Remove deprecated `compile()` and `compile_with_src_prefixes()` functions.

### v0.7.5
- Fix bug that prevented compilation of interfaces with generic superclasses.
- More robust error handling.

### v0.7.4
- Deprecate `compile()` and `compile_with_src_prefixes()` in favor of `CompilerCommand`.

### v0.7.3
- `capnpc -orust ./foo/bar/baz.capnp` now correctly writes to `./foo/bar/baz_capnp.rs` rather than
  just `./baz_capnp.rs`. If you were depending on the old behavior you can use the `--src-prefix`
  flag for finer-grained control of the output location.

### v0.7.2
- Nicer formatting for floating point literals.

### v0.7.1
- Fix bug that prevented pipelining on an AnyPointer field.