Housekeeping (#8)

* Rename the provider to dockerbuild.
* Add Makefile targets required by CI.
* Add per-language test targets compatible with CI.
* Fix broken example yaml.
* Add gitignore exclusions to fix SDK generation in CI.
* Fix lint errors.
* Vendor pulumi CLI via `tools.go` instead of `.pulumi`.
* Consolidate `go.mod`s into one file, with a minimal `go.mod` for the
Go SDK.
* Add codecov.

examples/java/src/main/java/generated_program/App.java

@@ -0,0 +1,27 @@
+package generated_program;
+
+import com.pulumi.Context;
+import com.pulumi.Pulumi;
+import com.pulumi.core.Output;
+import com.pulumi.dockerbuild.Random;
+import com.pulumi.dockerbuild.RandomArgs;
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Map;
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+public class App {
+    public static void main(String[] args) {
+        Pulumi.run(App::stack);
+    }
+
+    public static void stack(Context ctx) {
+        var myRandomResource = new Random("myRandomResource", RandomArgs.builder()        
+            .length(24)
+            .build());
+
+        ctx.export("value", myRandomResource.result());
+    }
+}