Remove native binarys and update instructions to use protoc jars about grpc-kotlin

[Octogonapus]

Now that google/protobuf-gradle-plugin#168 is closed, is it possible to implement this feature so that, ultimately, #116 can be fixed?

[jamesward]

Thanks for the heads up! That was actually closed as fixed :) So we won't need Canteen and can instead just use our protoc jars. Updating the title to reflect this.

[jamesward]

For reference: google/protobuf-gradle-plugin#423

[jamesward]

I think we should do a 0.2.0 release for this, migrate the samples & docs, and allow for good testing across platforms. Then once validated aim for 1.0.0.

Note that the syntax is:

artifact = "io.grpc:protoc-gen-grpc-kotlin:$grpcKotlinVersion:protoc@jar"

The classifier on the artifact in this case is protoc but I think there is some standard to instead make it like jdk8 for a JDK 8 compatiable jar.

[jamesward]

BTW, this requires a new version of the Gradle Protobuf plugin (0.8.13):

id("com.google.protobuf") version "0.8.13"

[jamesward]

The samples in this repo have been updated to use this. And here is the PR for updating the other kotlin samples: GoogleCloudPlatform/kotlin-samples#78