Implement Bazel build

TEST PLAN:
  $ bazel test gitiles-servlet/...

Run debug version:
  $ sh {path/to/src}/tools/run_bazel_dev.sh

TODO:

 * publishing maven artifacts.
 * check out Bazel's generate_workspace.
 * intellij/eclipse project generation

Change-Id: I288011ce622536ce72c59a1961f962db9fe9e761

lib/slf4j/BUILD

diff --git a/lib/slf4j/BUILD b/lib/slf4j/BUILD
new file mode 100644
index 0000000..4a27aac
--- /dev/null
+++ b/lib/slf4j/BUILD
@@ -0,0 +1,16 @@
+package(
+    default_visibility = ["//visibility:public"],
+)
+
+java_library(
+    name = "slf4j-api",
+    exports = ["@slf4j_api//jar"],
+)
+
+java_library(
+    name = "slf4j-simple",
+    runtime_deps = [
+        ":slf4j-api",
+        "@slf4j_simple//jar",
+    ],
+)