refactor: Make examples executable (#90)

Right now, the examples cannot be executed without manually linking NPM
modules to the correct locations, i.e. the `node_modules/` dir in
project root. This makes it really hard to just try out an example as a
user or as a developer working on opencensus-node.

This PR moves the example to a *private* module under `packages/`. This
means that lerna will automatically initialise the necessary symlinks
for developers working on this project. Users on the other hand, could
just run `npm install` and manually execute the examples.

packages/opencensus-example-automatic-tracing/package.json

@@ -0,0 +1,13 @@
+{
+  "name": "@opencensus/example-automatic-tracing",
+  "description": "These example show hot to trace a simple HTTP server and export the trace state.",
+  "version": "0.0.0",
+  "private": true,
+  "main": "zipkin.js",
+  "dependencies": {
+    "@opencensus/exporter-instana": "^0.0.3",
+    "@opencensus/exporter-stackdriver": "^0.0.3",
+    "@opencensus/exporter-zipkin": "^0.0.3",
+    "@opencensus/nodejs": "^0.0.3"
+  }
+}