Adding snippets for Datastore queries (GoogleCloudPlatform#181)

Author: Takashi Matsuo

datastore/api/README.md

@@ -17,4 +17,5 @@ To run the tests do the following:
 1. **Install dependencies** via [Composer](http://getcomposer.org/doc/00-intro.md).
     Run `php composer.phar install` (if composer is installed locally) or `composer install`
     (if composer is installed globally).
+1. Create Datastore indexes by running `gcloud preview datastore create-indexes index.yaml`
 1. Run `phpunit`

datastore/api/composer.json

@@ -1,9 +1,10 @@
 {
     "require": {
-        "google/cloud": "dev-master"
+        "google/cloud": "~1.0|~0.10"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.8"
+        "phpunit/phpunit": "~4.8",
+        "google/cloud-tools": "~1.0|~0.5"
     },
     "autoload": {
         "psr-4": { "Google\\Cloud\\Samples\\Datastore\\": "src" },