Twirp

This release includes a fix to the generator to support Protobuf messages that are not defined in camel case. For example, messages such as `Hat_v1` would have the Go type name `HatV1` in the protoc-gen-go generated code, but the Twirp generated code would expect `Hat_v1`.

A security vulnerability was discovered on the `requirements.txt` file that is used to test Python-generated code, and could be used as sub-dependency checks for Python projects using Twirp.

Fix submitted in this PR: https://github.com/twitchtv/twirp/pull/137

This release adds support for a new generator option, `paths=source_relative`, to match the behavior of the official protoc-gen-go generator. That behavior is documented at https://github.com/golang/protobuf/pull/533.

Now, `protoc-gen-twirp` can work outside of GOPATH to generate code. Files are output relative to where the proto source was found.

The change to make this possible is 126.

This is a bug fix release. It fixes 123.

Previously, if a service had a method of the same name, the generated Go code would not compile. For example, generated code for this service would not compile:
protobuf
service Echo {
rpc Echo(Msg) returns (Msg);
}


This was fixed in 124.

This release includes two bug fixes.

First, there was a bug in import statement generation when multiple `.proto` files were imported which shared an identical protobuf package, but which had different output go packages. This would most commonly occur when importing multiple "well-known type" definitions, like `google/protobuf/empty.proto` and `google/protobuf/wrappers.proto`. This was reported in 104, and fixed in 107.

Second, generated Go clients would previously return non-nil response types even when returning non-nil errors. This led to confusing behavior in some obscure cases, as users usually expect non-nil `error` to imply a nil response. This was fixed in 105.

This release includes 102, which adds support for flags for protoc-gen-twirp to map `.proto` files to particular Go import paths. This was requested in 13.

Documentation is available in https://github.com/twitchtv/twirp/blob/2d98ac4d4ccb29e08ea745c758e6d103f971eba5/docs/command_line.md, which is (as of this release) on the doc website at https://twitchtv.github.io/twirp/docs/command_line.html.