Modify the structure.

- the generated code will now export a function, which returns
  grpc and API class upon specified authentication context.
- v1beta1 also exports as a function, which builds API classes.
  (currently it's same as LanguageServiceApi itself, because
  language API is a single-service API).

The new usage would be:
```
var language = require('@google-cloud/language');
var v1beta1 = language.v1beta1({keyFile: ...});
var api = v1beta1.LanguageServiceApi();
api.annotateText({type: v1beta1.grpc.Document.Type.PLAIN_TEXT, ...});
```

packages/language/package.json

@@ -57,7 +57,7 @@
     "arguejs": "^0.2.3",
     "arrify": "^1.0.1",
     "extend": "^3.0.0",
-    "google-gax": "^0.5.2",
+    "google-gax": "^0.6.0",
     "google-proto-files": "^0.4.0",
     "is": "^3.0.1",
     "propprop": "^0.3.1",

packages/language/src/v1beta1/index.js

@@ -2,7 +2,10 @@
 
 var languageServiceApi = require('./language_service_api');
 
-exports.grpc = function(optGrpc) {
-  return languageServiceApi.grpc(optGrpc).google.cloud.language.v1beta1;
+function v1beta1(options) {
+  return languageServiceApi(options);
 };
-exports.languageServiceApi = languageServiceApi.LanguageServiceApi;
+
+v1beta1.SERVICE_ADDRESS = languageServiceApi.SERVICE_ADDRESS;
+v1beta1.ALL_SCOPES = languageServiceApi.ALL_SCOPES;
+module.exports = v1beta1;