Add Cloud Natural Language API sample. (#155)

* Add Cloud Natural Language API sample.

This sample makes a request to analyze the entities in text.

Change-Id: I387cff7ac70c6f3c00a5b213527b4bd71c6c44dc

* Update package.json

* Do it right this time

packages/google-cloud-language/samples/README.md

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+# Cloud Natural Language API Sample
+
+These samples demonstrate the use of the
+[Google Cloud Natural Language API](https://cloud.google.com/natural-language/docs/).
+
+`analyze.js` is a command-line program that demonstrates how different methods
+of the API can be called.
+
+## Setup
+
+Please follow the [Set Up Your Project](https://cloud-dot-devsite.googleplex.com/natural-language/docs/getting-started#set_up_your_project)
+steps in the Quickstart doc to create a project and enable the
+Cloud Natural Language API. Following those steps, make sure that you
+[Set Up a Service Account](https://cloud.google.com/natural-language/docs/common/auth#set_up_a_service_account),
+and export the following environment variable:
+
+```
+export GOOGLE_APPLICATION_CREDENTIALS=/path/to/your-project-credentials.json
+```
+
+## Run locally
+
+First install the needed dependencies.
+
+```
+npm install
+```
+
+To run:
+
+```
+node analyze.js <sentiment|entities|syntax> <text>
+```
+
+For example, the following command returns all entities found in the text:
+
+```
+node analyze.js entities "President Obama is speaking at the White House."
+```
+
+```
+{
+  "entities": [
+    {
+      "name": "Obama",
+      "type": "PERSON",
+      "metadata": {
+        "wikipedia_url": "http://en.wikipedia.org/wiki/Barack_Obama"
+      },
+      "salience": 0.84503114,
+      "mentions": [
+        {
+          "text": {
+            "content": "Obama",
+            "beginOffset": 10
+          }
+        }
+      ]
+    },
+    {
+      "name": "White House",
+      "type": "LOCATION",
+      "metadata": {
+        "wikipedia_url": "http://en.wikipedia.org/wiki/White_House"
+      },
+      "salience": 0.15496887,
+      "mentions": [
+        {
+          "text": {
+            "content": "White House",
+            "beginOffset": 35
+          }
+        }
+      ]
+    }
+  ],
+  "language": "en"
+}
+```

packages/google-cloud-language/samples/package.json

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+{
+  "name": "cloud-natural-language-api-samples",
+  "version": "1.0.0",
+  "description": "Samples for using the Google Cloud Natural Language API.",
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/GoogleCloudPlatform/nodejs-docs-samples.git"
+  },
+  "main": "analyze.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "dependencies": {
+    "googleapis": "^11.0.0"
+  },
+  "author": "Google, Inc.",
+  "license": "Apache-2.0"
+}