Add rest-credential.md to index.md & dropdown menu

docs/_includes/themes/zeppelin/_navigation.html

@@ -93,6 +93,7 @@
                 <li><a href="{{BASE_PATH}}/rest-api/rest-interpreter.html">Interpreter API</a></li>
                 <li><a href="{{BASE_PATH}}/rest-api/rest-notebook.html">Notebook API</a></li>
                 <li><a href="{{BASE_PATH}}/rest-api/rest-configuration.html">Configuration API</a></li>
+                <li><a href="{{BASE_PATH}}/rest-api/rest-credential.html">Credential API</a></li>
                 <li role="separator" class="divider"></li>
                 <li class="title"><span><b>Security</b><span></li>
                 <li><a href="{{BASE_PATH}}/security/authentication.html">Authentication for NGINX</a></li>

docs/index.md

@@ -163,6 +163,7 @@ Join to our [Mailing list](https://zeppelin.apache.org/community.html) and repor
   * [Interpreter API](./rest-api/rest-interpreter.html)
   * [Notebook API](./rest-api/rest-notebook.html)
   * [Configuration API](./rest-api/rest-configuration.html)
+  * [Credential API](./rest-api/rest-credential.html)
 * Security: available security support in Apache Zeppelin
   * [Authentication for NGINX](./security/authentication.html)
   * [Shiro Authentication](./security/shiroauthentication.html)

docs/rest-api/rest-credential.md

@@ -34,7 +34,7 @@ limitations under the License.
     <col width="200">
     <tr>
       <td>Description</td>
-      <td>This ```GET``` method return all key/value pair of credential informations on the server.</td>
+      <td>This ```GET``` method returns all key/value pairs of credential information on the server.</td>
     </tr>
     <tr>
       <td>URL</td>
@@ -78,7 +78,7 @@ limitations under the License.
     <col width="200">
     <tr>
       <td>Description</td>
-      <td>This ```PUT``` method create an credential information with new properties.</td>
+      <td>This ```PUT``` method creates an credential information with new properties.</td>
     </tr>
     <tr>
       <td>URL</td>