feat(deps): update-json using discovery API

Instead of depending on the google go client API repository, I now
use the original data source, namely the discovery API.

fixes #5

etc/api/content/v2/content-api.json

@@ -1,12 +1,12 @@
 {
  "kind": "discovery#restDescription",
- "etag": "\"ye6orv2F-1npMW3u9suM3a7C5Bo/C8XXsPv6OQ96WhF0iGLVjduwCpc\"",
+ "etag": "\"ye6orv2F-1npMW3u9suM3a7C5Bo/zR3ABmOvk7fZqleULAj42NskVkA\"",
  "discoveryVersion": "v1",
  "id": "content:v2",
  "name": "content",
  "canonicalName": "Shopping Content",
  "version": "v2",
- "revision": "20150218",
+ "revision": "20150311",
  "title": "Content API for Shopping",
  "description": "Manage product items, inventory, and Merchant Center accounts for Google Shopping.",
  "ownerDomain": "google.com",
@@ -154,6 +154,23 @@
     }
    }
   },
+  "AccountIdentifier": {
+   "id": "AccountIdentifier",
+   "type": "object",
+   "description": "Account identifier corresponding to the authenticated user.  \n- For an individual account: only the merchant ID is defined\n- For an aggregator: only the aggregator ID is defined\n- For a subaccount of an MCA: both the merchant ID and the aggregator ID are defined.",
+   "properties": {
+    "aggregatorId": {
+     "type": "string",
+     "description": "The aggregator ID, set for aggregators and subaccounts (in that case, it represents the aggregator of the subaccount).",
+     "format": "uint64"
+    },
+    "merchantId": {
+     "type": "string",
+     "description": "The merchant account ID, set for individual accounts and subaccounts.",
+     "format": "uint64"
+    }
+   }
+  },
   "AccountShipping": {
    "id": "AccountShipping",
    "type": "object",
@@ -676,6 +693,24 @@
     }
    }
   },
+  "AccountsAuthInfoResponse": {
+   "id": "AccountsAuthInfoResponse",
+   "type": "object",
+   "properties": {
+    "accountIdentifiers": {
+     "type": "array",
+     "description": "The account identifiers corresponding to the authenticated user.",
+     "items": {
+      "$ref": "AccountIdentifier"
+     }
+    },
+    "kind": {
+     "type": "string",
+     "description": "Identifies what kind of resource this is. Value: the fixed string \"content#accountsAuthInfoResponse\".",
+     "default": "content#accountsAuthInfoResponse"
+    }
+   }
+  },
   "AccountsCustomBatchRequest": {
    "id": "AccountsCustomBatchRequest",
    "type": "object",
@@ -2623,6 +2658,18 @@
  "resources": {
   "accounts": {
    "methods": {
+    "authinfo": {
+     "id": "content.accounts.authinfo",
+     "path": "accounts/authinfo",
+     "httpMethod": "GET",
+     "description": "Returns information about the authenticated user.",
+     "response": {
+      "$ref": "AccountsAuthInfoResponse"
+     },
+     "scopes": [
+      "https://www.googleapis.com/auth/content"
+     ]
+    },
     "custombatch": {
      "id": "content.accounts.custombatch",
      "path": "accounts/batch",