Fix some incompatible warnings and run buildifier (#1745)

Also: replace most calls to args.add_all([key, value]) with
args.add(key, value).
diff --git a/WORKSPACE b/WORKSPACE
index b636419..4be5594 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -1,5 +1,6 @@
 workspace(name = "io_bazel_rules_go")
 
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 load("@io_bazel_rules_go//go:def.bzl", "go_register_toolchains", "go_rules_dependencies")
 load("@io_bazel_rules_go//proto:def.bzl", "proto_register_toolchains")
@@ -9,10 +10,10 @@
 go_register_toolchains()
 
 # Needed for tests
-http_archive(
+git_repository(
     name = "bazel_gazelle",
-    sha256 = "c0a5739d12c6d05b6c1ad56f2200cb0b57c5a70e03ebd2f7b87ce88cabf09c7b",
-    urls = ["https://github.com/bazelbuild/bazel-gazelle/releases/download/0.14.0/bazel-gazelle-0.14.0.tar.gz"],
+    commit = "682c0e396e708a146e28f0796ae08b7913e2d9a9",  # master as of 2018-10-02
+    remote = "https://github.com/bazelbuild/bazel-gazelle",
 )
 
 load("@bazel_gazelle//:deps.bzl", "gazelle_dependencies")
@@ -48,11 +49,11 @@
 )
 
 http_archive(
-  name = "bazel_toolchains",
-  urls = [
-    "https://mirror.bazel.build/github.com/bazelbuild/bazel-toolchains/archive/cdea5b8675914d0a354d89f108de5d28e54e0edc.tar.gz",
-    "https://github.com/bazelbuild/bazel-toolchains/archive/cdea5b8675914d0a354d89f108de5d28e54e0edc.tar.gz",
-  ],
-  strip_prefix = "bazel-toolchains-cdea5b8675914d0a354d89f108de5d28e54e0edc",
-  sha256 = "cefb6ccf86ca592baaa029bcef04148593c0efe8f734542f10293ea58f170715",
+    name = "bazel_toolchains",
+    sha256 = "cefb6ccf86ca592baaa029bcef04148593c0efe8f734542f10293ea58f170715",
+    strip_prefix = "bazel-toolchains-cdea5b8675914d0a354d89f108de5d28e54e0edc",
+    urls = [
+        "https://mirror.bazel.build/github.com/bazelbuild/bazel-toolchains/archive/cdea5b8675914d0a354d89f108de5d28e54e0edc.tar.gz",
+        "https://github.com/bazelbuild/bazel-toolchains/archive/cdea5b8675914d0a354d89f108de5d28e54e0edc.tar.gz",
+    ],
 )