Adding bazel ci intergration

.ci/abseil-cpp.json

+// This is a relaxed JSON format, you can have comments in it.
+// This is a list of configuration for the job that does not specify a configuration.
+[
+    {"node": "linux-x86_64"},
+    {"node": "ubuntu_16.04-x86_64"},
+    {"node": "darwin-x86_64"}
+]