test/kvao: setup global.Promise on Node v0.10

When running the tests on Node v0.10, setup `global.Promise`
with Bluebird implementation. That way we don't have to run
this setup in the test suite of each kv connector.

test/kvao.suite.js

@@ -4,6 +4,9 @@ var debug = require('debug')('test');
 var fs = require('fs');
 var path = require('path');
 
+if (!global.Promise)
+  global.Promise = require('bluebird');
+
 module.exports = function(dataSourceFactory, connectorCapabilities) {
   describe('KeyValue API', function loadAllTestFiles() {
     var testRoot = path.resolve(__dirname, 'kvao');